19TH ANNUAL INTERNATIONAL ASTROPHYSICS CONFERENCE ORAL ABSTRACTS

Adhikari, Laxman Evolution of Entropy and Mediation of the Solar Wind by Turbulence Laxman Adhikari, CSPAR/UAH, USA Gary P. Zank, UAH/CSPAR, USA Lingling Zhao, CSPAR/UAH, USA Gary M. Webb, CSPAR/UAH, USA We study the evolution of solar wind entropy based on a conservative formulation of solar wind and turbulence transport model equations, and compare the model results to Voyager 2 measurements. For a polytropic index of γ = 5/3 (> 1), entropy increases with distance due to the dissipation of turbulence, being about 12.84% higher at 75 au than at 1 au. However, if the polytropic index satisfies γ < 1, entropy decreases. We show that not only the creation of pickup ions, but also stream‐shear leads to a decrease of the solar wind speed. We show that the sum of the solar wind flow energy (kinetic plus enthalpy) and turbulent (magnetic) energy is constant, indicating that kinetic solar wind energy is transferred into turbulent energy via stream‐shear and pickup ion isotropization, which then in turn heats the solar wind via the dissipation of turbulence. We compare the theoretical solutions of the solar wind entropy, the solar wind density, the thermal gas pressure, the solar wind proton temperature, and the fluctuating magnetic energy with those measured by Voyager 2. The results show that the theoretical results are in good agreement with the observed results. Asgari‐Targhi, An Observational Study of the Role of Flux Emergence, Flux Cancellation, and Non‐Potential Fields in the Heating of Active‐Region Loops Mahboubeh Mahboubeh Asgari‐Targhi, Harvard‐Smithsonian Center for Astrophysics, USA We study the high‐temperature (T>4 MK) emissions from mostly non‐flaring active regions using extreme ultraviolet images from the Atmospheric Imaging Assembly on the Solar Dynamic Observatory (SDO). We selected 48 active regions for detailed study. For each region, we measure the peak emission intensity in the Fe XVIII 94 A. This line is formed at a temperature of 7 MK, well above the peak of the differential emission measure distribution, so it represents high‐temperature emission produced by nanoflares. We also measure the total magnetic flux using the corresponding magnetograms from the Helioseismic and Magnetic Imager on SDO. We correlate the emission with other active‐region parameters such as the presence or absence of sunspots, non‐potential magnetic fields, and the emergence or cancellation of magnetic flux. We conclude that energy may be injected into the corona as a result of the dynamics of magnetic fields associated with sunspots and/ or emerging flux. Baker, Daniel Seven Years of Van Allen Probes Observations: Exploring the Sun‐Earth Connection D.N. Baker, University of Colorado Boulder, USA The Radiation Belt Storm Probes (RBSP) mission of NASA – later renamed the Van Allen Probes mission – came to its operational end in 2019 with the turning off of the RBSP‐A spacecraft in October 2019. From the time of launch in 2012, the more than seven years of observations from the RBSP sensors revealed a wealth of fascinating new features in the Earth’s radiation environs driven by solar and solar wind forcing events. In this presentation we examine the long run of energetic electron and proton data acquired by the dual RBSP sensor systems and we relate these results to the well‐observed features on the Sun that caused the near‐Earth responses. In this way, we demonstrate the immense progress that has resulted in our understanding of the “Sun‐Earth Connection” as a result of long‐ term synoptic observations. The measurements from the RBSP scientific sensors – a key part of NASA’s Living With a Star Program – reveal the immense benefits that would accrue from future continual monitoring with an operational version of the Van Allen Probes Mission. 19TH ANNUAL INTERNATIONAL ASTROPHYSICS CONFERENCE ORAL ABSTRACTS

Bellan, Paul How Solar and Astrophysical Eruptions Generate Energetic Particles, X‐rays, and Waves Paul Bellan, Caltech, USA Models for solar and astrophysical eruptions are based on MHD and always start with a twisted magnetic field, i.e., an electric current flowing along a magnetic flux tube. Unfortunately, MHD cannot explain the most outstanding feature of eruptions, namely bursts of energetic particles, X‐rays, and waves. Nevertheless, MHD is obviously relevant, because MHD explains very well what happens before these bursts. Caltech lab experiments relevant to solar and astrophysical eruptions similarly demonstrate MHD dynamics followed by non‐MHD bursts of X‐rays and waves. Detailed examination of these experiments and consideration of the incompressible nature of ideal MHD instabilities identifies a clear path from MHD dynamics to the non‐MHD physics responsible for particle energization, X‐rays, and wave bursts. In this path, a multi‐step sequence of MHD instabilities leads to reduction of the cross‐section of a twisted flux tube; this choking results either from Rayleigh‐Taylor rippling or from kinking stretching the flux tube length. Choking the flux tube cross‐section greatly increases the axial electric current density so the electron drift velocity constituting the electric current becomes so large as to drive a kinetic instability which then greatly increases the local resistivity. The experiments and theoretical analysis both show that kinetic instability happens when the flux tube cross‐section is reduced to be of the order of the ion skin depth. The high local resistivity resulting from the kinetic instability acts as an opening switch that interrupts the electric current and thereby causes a large inductive voltage drop V= L dI/dt that accelerates charged particles to high energy. The ion skin depth is the scale at which MHD fails because Hall and electron inertia terms become important. Since the ion skin depth is of the order of 10’s of meters in the solar corona, it is improbable that a nominal megameter solar flux tube could be squeezed to such a small scale. It is proposed that instead, a megameter solar flux tube (or equivalent astrophysical structure) is in reality composed of a rope‐like braid of successively smaller filamentary current‐carrying flux tubes having a fractal scaling, and that the smallest scale of these filaments become squeezed by MHD instabilities to the ion skin depth. The effect is like a rope breaking because its fine strands break. Boldyrev, Electron Temperature of the Solar Wind Stanislav Stanislav Boldyrev, University of Wisconsin‐Madison, USA As the solar wind plasma expands form the hot solar corona, its temperature drops. However, the radial temperature decline is much slower than that required by adiabatic cooling. We will discuss the results recently obtained in [1] and [2] on the electron distribution function and the electron temperature in the solar wind. First, we will characterize the electrons beam (the strahl) streaming from the corona along the magnetic field lined. Second, we will show that due to weak Coulomb collisions, the electrons are slowly scattered from the beam and heat the background plasma. We show that in the inner heliosphere, this process leads to a universal scaling law of the electron temperature with the distance, T(r) ~ r^‐2/5. [1] Stanislav Boldyrev & Konstantinos Horaites, Kinetic theory of the electron strahl in the solar wind, Monthly Notices of the Royal Astronomical Society, 489 (2019) 3412. [2] Stanislav Boldyrev, Cary Forest, & Jan Egedal, On the temperature of the solar wind, submitted (2019); arXiv:2001.05125. 19TH ANNUAL INTERNATIONAL ASTROPHYSICS CONFERENCE ORAL ABSTRACTS

Bower, Jonathan Compression and Shock Driven Variations of the Suprathermal He+ Pickup Ion Tail J. S. Bower, University of New Hampshire, USA E. Moebius, University of New Hampshire, USA A. Aly, University of New Hampshire, USA L. Berger, Christian Albrechts University of Kiel, Germany B. Klecker, Max‐Planck‐Institute for Extraterrestrial Physics, Germany M. Lee, University of New Hampshire, USA N. Schwadron, University of New Hampshire, USA We present a systematic analysis to determine variations in the suprathermal He+ pickup ion spectra, in solar wind compression regions, and around interplanetary shocks, shedding light on the acceleration mechanisms that generate suprathermal particle populations in the heliosphere. Suprathermal tails of solar wind and pickup ion populations have been widely observed throughout the heliosphere, surprisingly, even during quiet times when no other solar energetic particles are present. The spatial and temporal ubiquity of these tails, coupled with a characteristic power law spectra with v‐5 dependence in the solar wind frame, have led to a number of competing explanations as to their origin, ranging from the introduction of a new acceleration mechanism, driven by compressive fluctuations of the solar wind, to the superposition of power law, exponential, and Gaussian spectra from localized acceleration sources. Using STEREO‐A PLASTIC He+ observations, from 2007 to 2014, we expand on a superposed epoch analysis of the pickup ion distribution evolution across solar wind compressions to address variations of the suprathermal tail across compression regions and shocks. We find that the tail spectra and flux vary systematically across the compression region, and according to compression strength. The highest flux is observed inside the interaction region, with a magnitude that increases according to the solar wind speed gradient across the compression. In the compressed slow wind, these high fluxes are accompanied by strong tail spectra, close to v‐5, with generally softer spectra occurring in the fast wind. We find the lowest suprathermal flux in the center of the rarefaction region. While further verification is required, these observations appear largely consistent with theories of suprathermal tail generation and subsequent transport from compression and shock regions. Burlaga, Leonard Voyager 1 & 2 Observations of the Conversion of the Magnetic Fluctuations in the VLISM from Compressive Fluctuations near the Heliopause to Transverse Fluctuations Beyond L. Burlaga, NASA/GSFC, USA N. Ness, University of Maryland, UMBC, USA D. Berdichevsky, Trinnovum, LLC, USA L. Jian, NASA/GSFC, USA J. Park, NASA/GSFC; UMBC, USA A. Szabo NASA/GSFC, USA Voyager 2 (V2) crossed the heliopause at 119.0 AU on day 309, 2018, after which it observed compressive (magnetosonic) magnetic field fluctuations along the average magnetic field direction in the Very Local Interstellar Medium (VLISM) from day 309.7, 2018 to day 240.0629, 2019 at distances from 119.00 AU to 121.57 AU and latitudes 32.2° to 32.4° in heliographic inertial coordinates. Previously, Voyager 1 (V1) crossed the heliopause on day 238, 2012 at 121.55 AU and 35.0°N, and it also observed compressive magnetic field fluctuations, during a quiet interval between day 135, 2013 and day 232, 2014, ∼2‐7 AU upwind of the heliopause (between 124.16 AU and 128.68 AU) at 35°N [1]. It was suggested that these compressive magnetic field fluctuations might have been transmitted across the heliopause into the VLISM from the heliosheath, where the magnetic fluctuations are known to be compressible [2]. It was shown theoretically that magnetic fluctuations in the heliosheath can only be converted to compressive fluctuations in the VLISM [3]. Thus, it came as a surprise to find that V1 observed transverse (Alfvenic) fluctuations of B from day 145, 2015 to day 248, 2016 when V1 was in the region between ∼9‐14 AU upwind of the heliopause (located between 131.40 AU and 135.98 AU) at latitude 35°N [4]. It was suggested that despite the weak nature of the fluctuations this transformation was probably real, but further observations were needed to confirm this [4]. The most recent V1 observations, in a relatively undisturbed interval between day 75, 2018 and day 178, 2019 were also transverse fluctuations in B at larger distances from the heliopause (141.44 AU to 146.01 AU, at 35.1°N) consistent with the view that the fluctuations in the VLISM should be Alfvenic. Thus, the observations show that compressive MHD fluctuations near the heliopause in the VLISM can be converted into transverse fluctuations, consistent with a theory of the mode‐conversion process [5]. [1] Burlaga et al. ApJ Lett. 804, L31 2015 [2] Burlaga et al. Journal of Physics: Conference Series 642 2015 [3] Zank et al. ApJ 842 113 2017 [4] Burlaga et al. 2018 ApJ 854 20 2018 [5] Zank et al. ApJ 887 116 2019 19TH ANNUAL INTERNATIONAL ASTROPHYSICS CONFERENCE ORAL ABSTRACTS

Bzowski, Maciej How to Model the Heliosphere to Analyze Various Populations of Atoms M. Bzowski, Space Research Centre PAS (CBK PAN), Poland M.A. Kubiak, Space Research Centre PAS (CBK PAN), Poland Interaction between the solar wind and the local interstellar environment has been studied using several observation techniques, including in‐situ sampling of the plasma, magnetic field, and energetic ions by the Voyager spacecraft; remote‐sensing observations of ENAs (energetic neutral atoms; IBEX, Cassini); and the primary and secondary populations of ISN (interstellar neutral) gas (IBEX‐Lo). Understanding the processes at the heliospheric boundary and of the conditions outside the heliosphere is typically done by fitting parameters used in models of the heliosphere to various observables. These observables include, e.g., the Voyager crossing distances of the termination shock and the heliopause, the size and the center of the IBEX ribbon, the sky distribution of the Lyman‐α helioglow, and the directly sampled flux of ISN gas at 1 au. Typically, it is expected that all or most of these observables are reproduced, a goal still not achieved. Application of the existing state of the art models of the heliosphere for determination of various subsets of LISM parameters based on various subsets available data resulted in significantly different estimates of the LISM parameter values (cf. Zirnstein et al. 2016 and Bzowski et al. 2019 on one hand and Izmodenov & Alexashow 2020 on the other hand). Even though the interaction of interstellar neutral gas with the solar wind and solar EUV output inside the termination shock is sometimes taken into account, the global heliosphere is usually simulated as a stationary structure, with the solar wind flux, density, and magnetic field variation ignored. However, solar wind is a dynamic phenomenon, which results in variations in the plasma flow both inside and outside the heliopause and in variations of the termination shock and the heliopause. The important issues are (1) how accurate are physical models used in the model simulations (e.g., the charge exchange cross sections), (2) what is the time span that a time dependent simulation must cover to match the time interval between the production of particle populations in their source regions and the observation, and (3) how accurate are results of analyses performed using a stationary approximation. (1) The uncertainty in the charge exchange cross section for H – p collision speeds characteristic for the OHS (outer heliosheath), rooted in disparate measurements, results in considerable uncertainties in the plasma speeds, densities, and temperature distributions in the OHS, and consequently in the secondary and the filtered primary populations of ISN H. Also, the shape and the size of the heliosphere are affected. (2) The flight times of various particle populations between the respective source regions and the detectors at 1 au are very different: from a year for GDF ENAs to 3—4 solar cycles for the primary‐population ISN atoms to ~15 solar cycles for the secondary ISN atoms, with spreads of about half of these values. These latter large delays are characteristic for ISN species sampled by IBEX, but also for the Lyman‐α helioglow measurements performed from 1 au. This implies that (a) the state of the heliosphere diagnosed using atoms with different energies is characteristic for different, non‐overlapping time intervals, and (b) a time dependent model of the heliosphere needs to cover about 2 – 3 solar cycles for analyses of GDF ENAs and the IBEX Ribbon, but at least 15 solar cycles for analyses of the secondary ISN gas‐related observables. (3) While time‐dependent models of the heliosphere with observation‐based solar wind conditions exist, the time span of available solar wind data is only sufficient to address the ENA observations, but not the ISN gas populations. Hence, only stationary models of the heliosphere with appropriately averaged solar wind parameters are presently available to simulate the heliospheric boundary region for the needs of observations of ISN gas. Nevertheless, the solar forcing modifying the atom flux deep inside the termination shock needs to be taken into account. In summary, the ISN and ENAs bring information on the heliosheath from vastly disparate epochs. This is a challenge for measurement interpretation, but also an opportunity for doing interesting science. 19TH ANNUAL INTERNATIONAL ASTROPHYSICS CONFERENCE ORAL ABSTRACTS

Che, Haihong Electron Acceleration From Expanding Magnetic Vortices During Reconnection with a Guide Field H. Che, University of Alabama in Huntsville, USA G.P. Zank, University of Alabama in Huntsville, USA Magnetic reconnection is believed to be responsible for the acceleration of energetic electrons with a power‐law spectrum in the solar wind and solar flares. However, recent studies of the leading mechanism of electron acceleration in reconnection, namely, acceleration by tearing instability induced multi‐islands, demonstrates that this mechanism suffers from an "injection problem" for mildly relativistic reconnection acceleration. In this paper we investigate a new type of reconnection acceleration in which an electron Kelvin‐Helmholtz instability (EKHI) is driven as the current sheet reaches electron inertial length scales during magnetic reconnection with a strong guide field. Electrons are accelerated by stochastic electric fields, induced by the EKHI generated vortices that expand rapidly, and a power‐law electron energy spectrum $f(W) \propto W^{‐\alpha}$ with index $\alpha\sim 3.5$ is produced ($W$ is the electron kinetic energy and $f(W)$ is the energy distribution function.) We show that the mechanism is a 2nd‐order Fermi acceleration process, and the index $\alpha = (1+4 a^2 D/R)/2 $ where $a= B_g/B_0$, which is determined by the ratio of the spatial scale of the inductive electric field $D$ to that of vortices $R$ and the ratio of guide field $B_g$ to asymptotic magnetic field $B_0$. Chen, Yu Small‐scale Magnetic Flux Ropes in the Solar Wind: from 0.17 to 8 au Yu Chen, University of Alabama in Huntsville, USA Qiang Hu, University of Alabama in Huntsville, USA Since the completion of the first two orbits of the Parker Solar Probe (PSP), several types of structures in the solar wind at close distances to the Sun have been reported via observational studies, such as coronal mass ejections (CMEs), Alfvenic structures, switchbacks, and magnetic flux ropes, etc. In this study, we mainly focus on the small‐scale magnetic flux ropes (SFRs) and their properties at radial distances around the first two perihelions. The Grad‐Shafranov‐reconstruction‐based detection is applied to identify SFRs from in‐situ measurements automatically. We present the temporal distributions and scale size parameters of these identified SFRs. Several events, which were reported earlier in other studies by using totally different methods and are also detected in this study, are described by deriving their cross‐section configurations and compared in detail. We also present the evolution of SFR properties with the change of heilocentric distances (from ~ 0.17 au to ~ 8 au) by comparing with the existing SFR databases obtained via the Helios, ACE, Ulysses, and Voyager spacecraft datasets. Chhabra, Sherry Study of Type III Solar Radio Bursts in Nanoflares Sherry Chhabra, NJIT/NASA‐GSFC, USA James A. Klimchuk, NASA‐GSFC, USA Dale E. Gary, New Jersey Institute of Technology, USA Nicholeen M. Viall, NASA‐GSFC, USA The heating mechanisms responsible for the million‐degree solar corona remain one of the most intriguing problems in space science. It is widely agreed, that the ubiquitous presence of reconnection events and the associated impulsive heating (nanoflares) are a strong candidate in solving this problem [Klimchuk J.A., 2015 and references therein]. Whether nanoflares accelerate energetic particles like full‐sized flares is unknown. The lack of strong emission in hard X‐rays suggests that the quantity of highly energetic particles is small. There could, however, be large numbers of mildly energetic particles (~ 10 keV). We investigate such particles by searching for the type III radio bursts that they may produce. If energetic electron beams propagating along magnetic field lines generate a bump‐on‐tail instability, they will produce Langmuir waves, which can then interact with other particles and waves to give rise to emission at the local plasma frequency and its first harmonic. Type III bursts are characteristically known to exhibit high frequency‐drifts as the beam propagates through a density gradient. The time‐lag technique that was developed to study subtle delays in light curves from different EUV channels [Viall & Klimchuk 2012] can also be used to detect subtle delays at different radio frequencies. We have modeled the expected radio emission from nanoflares, which we used to test and calibrate the technique. We are applying the technique to actual radio observations from VLA (Very Large Array), MWA (Murchison Widefield Array) and seeking data from LOFAR (Low‐Frequency Array) as well. We are also using data from the PSP (Parker Solar Probe) to look for similar reconnection signatures in the Solar Wind. Our goal is to determine whether nanoflares accelerate energetic particles and to determine their properties. The results will have important implications for both the particle acceleration and reconnection physics. 19TH ANNUAL INTERNATIONAL ASTROPHYSICS CONFERENCE ORAL ABSTRACTS

Christian, Eric PSP/IS0IS Observations of Energetic Particles in the Inner Heliosphere Eric R. Christian, NASA/GSFC, USA David J. McComas, Princeton U., USA Mark E. Wiedenbeck, Caltech/JPL, USA Ralph L. McNutt, JHU/APL, USA Nathan. A Schwadron, UNH, USA Christina M.S. Cohen, Caltech, USA Alan C. Cummings, Caltech, USA Andrew J. Davis, Caltech, USA Georgia A. de Nolfo, NASA/GSFC, USA Mihir I. Desai, SwRI San Antonio, USA Joseph Giacalone, U. Arizona, USA Matt E. Hill, JHU/APL, USA Colin J. Joyce, Princeton U., USA Stamatios M. Krimigis, JHU/APL, USA Allan W. Labrador, Caltech, USA Richard A. Leske, Caltech, USA Olga Malandraki, Nat. Obs.of Athens, Greece William H. Matthaeus, U. of Delaware, USA Richard A. Mewaldt, Caltech, USA Donald G. Mitchell, JHU/APL, USA John G. Mitchell, NASA/GSFC/GWU, USA Arik Posner, NASA/HQ, USA Jamie S. Rankin, Princeton U., USA Edward C. Roelof, JHU/APL, USA Edward C. Stone, Caltech, USA Jamey R. Szalay, Princeton U., USA Stuart D. Bale, UCBerkeley, USA Justin C. Kasper, UMichigan, USA Anthony W. Case, SAO, USA Kelly E. Korreck, SAO, USA Robert J. MacDowall, NASA/GSFC, USA Marc Pulupa, UCBerkeley, USA Michael L. Stevens, SAO, USA Alexis P. Rouillard, CNRS, France The Parker Solar Probe (PSP) mission, launched on August 12, 2018, has been investigating the inner heliosphere under Solar Minimum conditions. Although the Sun has been very quiet, the Integrated Science Investigations of the Sun (IS0IS) instrument suite on PSP has observed a number of small solar energetic ion and electron events from closer to the Sun than any previous spacecraft. The time profiles, spectra, composition, and anisotropy of these events will be presented, and any association with solar activity will be examined. The new observations from PSP will be very important to our understanding of the acceleration and transport of solar energetic particles. 19TH ANNUAL INTERNATIONAL ASTROPHYSICS CONFERENCE ORAL ABSTRACTS

Consolini, On the Scaling Properties of Magnetic and Electric Field Fluctuations in the Solar Wind Giuseppe G. Consolini, INAF‐IAPS, Italy T. Alberti, INAF‐IAPS, Italy M. Stumpo, Univ. of Rome Tor Vergata, and INAF‐IAPS, Italy E. Yordanova, Swedish Institute of Space Physics, Sweeden M.F. Marcucci, INAF‐IAPS, Italy V. Carbone, Univ. of Calabria, Italy P. De Michelis, INGV, Italy Turbulence, intermittency, and self‐organized structures in space plasmas can be investigated by using a multifractal formalism mostly based on the canonical structure function analysis with fixed constraints about stationarity, linearity, and scales. Here, we present a double approach to the characterization of the multifractal nature of the magnetic and electric fields’ fluctuations in both the inertial and dissipative domains using measurements from ESA‐Cluster mission. In particular, the Empirical Mode Decomposition (EMD) method is firstly used to investigate timescale fluctuations of magnetic and electric fields in the solar wind, by exploiting the local properties of fluctuations; then, the structure function analysis is used to gain insights into the scaling properties of both inertial and kinetic/dissipative ranges. Finally, an analysis of the joint multifractal features in the inertial range is also done using canonical measure analysis. The results show that magnetic field fluctuations within the inertial range can be described in a multifractal framework, characterizing an unstable fixed point of the system, while a monofractal description allows to describe magnetic field fluctuations in the kinetic/dissipative range. Similar results are found for the electric field fluctuations within the inertial range, while deeper investigations are needed to provide a proper fractal description of their dissipative nature. Cummings, Alan Interaction of Heliosphere with the Interstellar Medium: Cosmic Ray Results A. C. Cummings, Caltech, USA E. C. Stone, Caltech, USA B. C. Heikkila, GSFC, USA N. Lal, GSFC, USA The two Voyager spacecraft crossed the heliopause into interstellar space in very different positions. Voyager 1 (V1) crossed on 25 August 2012 at 121.6 AU from the Sun, at a solar ecliptic latitude of 35 degrees N, and at 255 degrees in ecliptic longitude. Voyager 2 (V2) crossed on 5 November 2018 at 119.0 AU from the Sun, at a latitude of 36.5 degrees S, and at 290.3 degrees in longitude. V1 crossed near the nose of the heliosphere, whereas V2 crossed at a position 35.3 degrees further back along the flank. There were both similarities and differences in these crossings as observed in the data from the Cosmic Ray Subsystem instrument on each spacecraft. We will present some of the cosmic ray results from these crossings, highlighting some of the similarities and differences. We will also present recent observations from V2 of perhaps a new type of event in the local interstellar medium. This work was supported by NASA under grant NNN12AAO1C. Dagnew, A Comparison of CME Expansion Speeds Between Solar Cycles 23 and 24 Fithanegest Fithanegest Kassa Dagnew , Ethiopian Space Science and Technology Institute (ESSTI), Ethiopia, NASA Goddard Space Flight Center, and The Catholic University of America, USA Nat Gopalswamy , NASA Goddard Space Flight Center, USA Solomon Belay Tessema, Ethiopian Space Science and Technology Institute (ESSTI), Ethiopia We report on a comparison of the expansion speeds of limb coronal mass ejections (CMEs) between solar cycles 23 and 24. We selected a large number of limb CME events associated with soft X‐ray flare size greater than or equal to M5.0 from both cycles. We used data and measurement tools available at the online CME catalog (https://cdaw.gsfc.nasa.gov) within the SOHO/LASCO C2 and C3 fields of view. We found that the expansion speeds in cycle 24 are significantly higher than those in cycle 23. We also found that the relation between radial and expansion speeds has different slopes in cycles 23 and 24. The cycle 24 slope is 44% higher than that in cycle 23. The expansion speed is higher for a given radial speed. The difference increases with speed. For a 2000 km/s radial speed, the expansion speed in cycle 24 is ~29% higher. These results present additional evidence for the anomalous expansion of cycle 24‐CMEs, which is due to the reduced total pressure in the heliosphere. 19TH ANNUAL INTERNATIONAL ASTROPHYSICS CONFERENCE ORAL ABSTRACTS

Dayeh, Maher Effects of the sampling window on the relation between the shock compression ratio and the accelerated particle spectrum in energetic storm particle (ESP) events Maher Dayeh, Southwest Research Institute, USA Kim Moreland, University of Texas at San Antonio, USA Mihir Desai, Southwest Research Institute, USA Rob Ebert, Southwest Research Institute, USA Lan Jian, NASA Goddard Space Flight Center, USA Gang Li, University of Alabama in Huntsville, USA Lulu Zhao, Florida Institute of Technology, USA

Energetic storm particle (ESP) events are sudden enhancements of energetic particles (> 10s of keV/nucleon) observed in association with the passage of shocks driven by interplanetary (IP) coronal mass ejections (ICMEs). ESPs can produce significant increases in the near‐Earth particulate radiation and pose severe hazards to astronauts and hardware in space. The primary candidate for producing ESPs is diffusive shock acceleration (DSA) at the IP shock. While DSA offers a plausible prediction of ESP signatures near 1 AU, observations do not agree with DSA predictions for most cases. In this study, we use data from plasma and energetic particle instruments onboard ACE to examine the effects of the downstream and upstream sampling window on the inferred shock and ESP properties in ~300 events. We particularly focus on the relation between the shock compression ratio and the spectral index of the accelerated spectrum. Du, Senbei Energy Dissipation and Entropy in Collisionless Plasma Senbei Du, University of Alabama in Huntsville, USA Gary P. Zank, University of Alabama in Huntsville, USA Xiaocan Li, Los Alamos National Laboratory, USA Fan Guo, Los Alamos National Laboratory, USA It is well known that collisionless systems are dissipation free from the perspective of particle collision and thus conserve entropy. On the other hand, processes such as magnetic reconnection and turbulence appear to convert large‐scale magnetic energy into heat. We investigate the energization and heating of collisionless plasma. The dissipation process is discussed in terms of fluid entropy in both isotropic and gyrotropic forms. Evolution equations for the entropy are derived and they reveal mechanisms that lead to changes in fluid entropy. These equations are verified by a collisionless particle‐in‐cell simulation of multiple reconnecting current sheets. In addition to previous findings regarding the pressure tensor, we emphasize the role of heat flux in the dissipation process. 19TH ANNUAL INTERNATIONAL ASTROPHYSICS CONFERENCE ORAL ABSTRACTS

Elliott, Heather Slowing of the Solar Wind In the Outer Heliosphere Heather A. Elliott, Southwest Research Institute, USA David J. McComas, Princeton University, USA Eric J. Zirnstein, Princeton University, USA Brent M. Randol, Goddard Space Flight Center, USA Peter A. Delamere, University of Alaska, USA George Livadiotis, Southwest Research Institute, USA Fran Bagenal, University of Colorado, USA Nathan P. Barnes, University of Alaska, USA S. Alan Stern, Southwest Research Institute, USA Leslie A. Young, Southwest Research Institute, USA Catherine B. Olkin, Southwest Research Institute, USA John Spencer, Southwest Research Institute, USA Harold A. Weaver, Applied Physics Lab, USA Kimberly Ennico, NASA Ames, USA G. Randall Gladstone, Southwest Research Institute, USA Charles W. Smith, University of New Hampshire, USA This study provides a deeper understanding of how the solar wind evolves with increasing distance from the Sun as it encounters an increasing amount of interstellar material. This work extends our prior work by (1) extending the solar wind proton data radial profiles for New Horizons (NH) out to nearly 43 au, (2) quantifying the observed amount of slowing in the solar wind in the outer heliosphere by performing a detailed comparison between the speeds at NH (21–43 au) with speeds at 1 au, and (3) resolving discrepancies between the measured amount of slowing and estimates of the amount of slowing determined from the measured amount of interstellar pickup present in the solar wind. We find that the solar wind density radial profile may decrease at nearly or slightly less than a spherical expansion density profile. However, the temperature profile is well above what would be expected for an adiabatic profile. By comparing outer and inner heliospheric solar wind observations, we find the solar wind speed is reduced by 5%–7% between 30 and 43 au. We find the solar wind polytropic index (γsw) steeply decreases toward zero in the outer heliosphere (21–43 au) with a slope of ∼0.031 au−1. Using both this radial variation in γsw and the measured amount of interstellar pickup ions, we estimate the slowing in the solar wind and obtain excellent agreement with the observed slowing. Fraternale, Waves and Turbulence in the Local Interstellar Medium Federico Federico Fraternale, University of Alabama in Huntsville, USA Nikolai V Pogorelov, University of Alabama in Huntsville, USA Tae Kim, The University of Alabama in Huntsville, USA The Local Interstellar Medium (LISM) observed by the Voyager 1 spacecraft since August 2012 exhibits broadband spectrum of fluctuations over a vast range of scales, whose nature is an intriguing topic. Two‐year periodic shocks of heliospheric origin were found to be a prominent feature of the LISM, able to trigger plasma waves and GCR anisotropy. This study presents a multi‐scale analysis of magnetic field increments of LISM fluctuations at V1 during 2012.6‐2019.0. We focus attention on coherent wave trains with integral scale in the range 25‐100 days (spacecraft frame) and other structures resembling rotational discontinuities, that seem responsible for spectral breaks in the statistics and skewed probability density functions. These wave trains may constitute an energy reservoir for the turbulent cascade at higher frequencies. The interaction of shocks with the turbulent magnetic field is discussed in terms of fluctuation's intensity, anisotropy and correlation scales. 19TH ANNUAL INTERNATIONAL ASTROPHYSICS CONFERENCE ORAL ABSTRACTS

Fu, Xiangrong Compressible Turbulence in the Solar Wind near the Sun Xiangrong Fu, New Mexico Consortium, USA Hui Li, John Steinberg and Diana Swanson, Los Alamos National Laboratory, USA Solar wind turbulence is nearly incompressible near 1 AU, as shown by many in‐situ measurements. However, when it gets closer to the Sun, transonic fluctuations (with fluctuating velocity close to sound speed) drive significantly more compressible turbulence, characterized by enhanced density fluctuations. By analyzing observations from the first two orbits of Parker Solar Probe, we show that the turbulence is nearly incompressible during quiet times, while it could be more compressible during perturbed times such as switchbacks. These measurements are compared to results from 3D MHD simulations of driven turbulence, where properties of compressible turbulence and its dependence on plasma beta, turbulent Mach number and types of driving are studied. Compressible turbulence may need to be included in global solar wind models because it dissipates differently from incompressible turbulence and could heat the solar wind more efficiently.

Fuselier, Stephen ENA Fluxes from the Inner Heliosheath: Constraints from in situ Measurements S. A. Fuselier, Southwest Research Institute, University of Texas at San Antonio, USA A. Galli, University of Bern, Switzerland J. D. Richardson, Massachusetts Institute of Technology, USA D. B. Reisenfeld, Los Alamos National Laboratory, USA M. A. Dayeh, Southwest Research Institute, USA N. A. Schwadron, University of New Hampshire, USA D. J. McComas, Princeton University, USA H. A. Elliott, Southwest Research Institute, USA IBEX observes ENA fluxes from the heliosphere over the energy range from 0.01 to 6 keV. In addition to the relatively narrow, circular region of enhanced emissions, called the IBEX Ribbon, IBEX observes a diffuse ENA flux from all directions, called the globally distributed flux (GDF). One of these directions is the line‐of‐sight of the Voyager 2 trajectory. Now that Voyager 2 has crossed the heliopause, there is a continuous record of the shocked solar wind plasma parameters spanning the entire inner heliosheath from the termination shock to the heliopause. This talk focuses on the constraints that these and other in situ plasma measurements place on the IBEX ENA fluxes from that line‐of‐sight direction. Particular focus is on constraints on low energy (<0.2 keV) ENA fluxes. Gary, S. Peter Particle‐in‐Cell Simulations of Kinetic Range Turbulence: Three Big Questions S. Peter Gary, Space Science Institute, USA Particle‐in‐cell (PIC) simulations are important tools for understanding the dissipation associated with the forward cascade of kinetic range turbulence in homogeneous, magnetized, collisionless plasmas. Recent PIC simulations have produced substantial new results, but have also raised new fundamental questions. In this presentation I pose three questions which I believe should be addressed by future PIC computations. 1) What geometry in 2.5D simulations gives the best approximation to the more complete 3D simulations of homogeneous plasma turbulence? 2) Are there relatively simple analytic scaling relations for the rates of electron and ion dissipation as functions of the plasma parameters of collisionless turbulence? and 3) Why does linear theory of ion anisotropy instabilities in homogeneous plasmas predict instability thresholds correlated with those obtained from PIC simulations of strongly inhomogeneous plasma turbulence? I will present no definitive answers, but will rather suggest a program of PIC simulations which may lead to an increased understanding of these issues. 19TH ANNUAL INTERNATIONAL ASTROPHYSICS CONFERENCE ORAL ABSTRACTS

Giacalone, Joe Acceleration of Protons from the Secondary Beam Component of the Solar Wind Distribution: Implications for Particle Acceleration Joe Giacalone, University of Arizona, USA The thermal portion of the solar wind proton distribution is often observed to have two components: a primary “core” component, and a less dense, secondary beam component. The beam component moves relative to the core with speeds of the order of the Alfven speed, or more, in a direction aligned with the magnetic field. The two‐ component (thermal) solar‐wind proton distribution is occasionally seen at 1AU, and is more commonly observed closer to the Sun. Relative to the core, the secondary beam is suprathermal, and, as such, can be more‐efficiently accelerated by shock waves, for example, than the particles in the core which must overcome a so‐called “injection threshold”. Thus, the suprathermal tail seen in proton distributions in space, yet another component of the overall proton spectrum could potentially consist mostly of particles from the beam component in some cases. We investigate this effect using numerical simulations, including fully self‐consistent hybrid simulations and kinematic test‐ particle simulations. Implications for understanding the source of high‐energy particles in the inner heliosphere, and the implications for future spacecraft observations, such those from NASA/ IMAP, as well as the general physics of this process will be discussed. Gladstone, Randy New Horizons UV Observations of the Interplanetary and Local Interstellar Medium G. Randall Gladstone, Southwest Research Institute, USA Wayne M. Pryor, Central Arizona College, USA Joshua A. Kammer, Southwest Research Institute, USA Kurt D. Retherford, Southwest Research Institute, USA Leslie A. Young, Southwest Research Institute, USA Andrew J. Steffl, Southwest Research Institute, USA Joel Wm. Parker, Southwest Research Institute, USA Carey M. Lisse, The Johns Hopkins University, USA Harold A. Weaver, The Johns Hopkins University, USA Kelsi N. Singer, Southwest Research Institute, USA John R. Spencer, Southwest Research Institute, USA S. Alan Stern, Southwest Research Institute, USA The Alice spectrograph on the New Horizons (NH) spacecraft is used to observe the Lyman‐alpha (Lya) interplanetary medium (IPM) background, which results from resonant scattering of solar Lya emissions by interstellar hydrogen atoms as they pass through the solar system. Observations of IPM Lya along 6 great circles spread over the entire sky at intervals of 30 degrees have been acquired about every 6 months since the NH flyby of Pluto. These observations have demonstrated that the IPM background at Lya is consistent with observations made three decades earlier by the UVS instruments on Voyager 1 and 2; furthermore, the data indicate a more distant galactic Lya background of about 40 Rayleighs brightness. In addition to Lya emissions, relatively deep (1‐hour) Alice spectra near the upstream and downstream directions of the interstellar wind are acquired along with the great circle data, and these constrain the brightness of other resonance line emissions, placing limits on the IPM abundances of interstellar C, N, and O atoms. Details of these results and plans for future observations will be presented here. This research was supported by NASA contract NASW02008 to SwRI. Golla, Thejappa Detection of Extreme and Exceptional Langmuir Wave packets in Solar Type III Radio Bursts G. Thejappa, University of Maryland, USA R. J. MacDowall, NASA/ Goddard Space Flight Center, USA We report the detection of two extreme and exceptional Langmuir wave packets in the source regions of solar type III bursts by the STEREO spacecraft. These are the most intense wave packets ever detected so far; their peak intensities 215 mV/m and 161 mV/m beat out the previous 107 mV/m record. We show that these wave packets provide new evidence for (1) the four wave interaction called the oscillating two stream instability (OTSI), which is the coupling of two beam‐excited Langmuir waves with an ion‐sound wave yielding down‐ and up‐shifted sidebands, and (2) the collapsing as well as quasi‐stable Langmuir solitons formed as a result of OTSI, and (3) density cavities created by their ponderomotive forces. We also show that the FFT spectra of these wave packets provide what is believed to be the first evidence for harmonics of the electron plasma frequency, up to the order of 5 with peak intensities falling off with increasing harmonic number. With the help of higher order spectral analysis, we demonstrate that these harmonics probably correspond to the electromagnetic waves excited as a result of various three wave interactions. Although the observed characteristics also indicate that these wave packets could be the collapsing wave packets formed as a result of nucleation instability, the observed evidence for OTSI and Langmuir solitons trapped inside the self‐generated density cavities strongly favor the OTSI as the route for the spatial collapse of Langmuir waves. 19TH ANNUAL INTERNATIONAL ASTROPHYSICS CONFERENCE ORAL ABSTRACTS

Gopalswamy, Nat Change in the State of the Heliosphere Revealed by Halo Coronal Mass Ejections Nat Gopalswamy, NASA Goddard Space Flight Center, USA Sachiko Akiyama, Catholic University, USA Grzegorz Michalek, Jagiellonian University, Poland Seiji Yashiro, Catholic University, USA The small solar cycle 24 resulted in a weak state of the heliosphere that led to the paucity of high‐energy solar energetic particle events and weak geomagnetic storms. The appearance of coronal mass ejections (CMEs) drastically changed with increased width near the Sun and higher abundance of halo CMEs. Based on the observation that CMEs had higher width near the Sun but lower magnetic cloud size at 1 AU, Gopalswamy et al. (2015, JGR 120, 9221) suggested that cycle‐24 CMEs must be attaining pressure balance with the ambient medium at larger heliocentric distances than in cycle 24. Observationally, this means that cycle‐24 CMEs attain their maximum width at a larger heliocentric distance than in cycle 23. In order to test this, we consider all frontside halo CMEs observed by the Large Angle and Spectrometric Coronagraphs (LASCO) on board the Solar and Heliospheric Observatory (SOHO) in solar cycles 23 and 24 and determine at what heliocentric distance they become halos. Since the true height of halo CMEs is unknown, we simply determine whether they become halos in the inner or outer telescope field of view. LASCO C2 and C3 telescopes have field of view (FOV) in the range 2.5 to 6 Rs and 3 to 32 Rs, respectively. The transition between the two FOVs roughly correspond to the heliocentric distance at which CMEs attain their maximum width. Therefore, we divided the halos into C2 halos and C3 halos based on the FOV in which they become halos for the first time. We find that in cycle 24 there are more C3 halos than in cycle 23, while the other way around for C2 halos. For example, there were 204 and 142 frontside halos, respectively in cycles 23 and 24 within a central meridian distance of 80 degrees. Only 47% were C3 halos in cycle 23 compared to 61% in cycle 24. This result strongly supports the prediction that CMEs attain pressure balance with the ambient medium at larger heliocentric distances in cycle 24 due to the reduced ambient total pressure. Guo, Xiaocheng Statistical Investigation on the Galactic Cosmic Rays and Solar Wind Variation based on ACE Observations Xiaocheng Guo, National Space Science Center, CAS, China Galactic cosmic rays (GCRs) are modulated by the heliospheric magnetic field when they enter the heliosphere. Based on the GCR and plasma observations from ACE spacecraft, we analyzed the relation between the GCR counts and the solar wind parameters during the recent two periods of solar minimum (the years of 2007.0‐2009.0 and 2016.5‐2019.0) by means of the super epoch analysis method. The results indicate that GCRs are strongly modulated by the corotating interaction regions (CIRs) in solar wind, the stream interfaces (SIs) sandwiched between fast and slow solar wind are closely related with the depression of GCR counts. The mechanism of the GCR variation is investigated through the empirical diffusion coefficients. The so‐called “snow‐plough” effect of GCR variation prior to the SI crossing appears during the first period, then the GCR counts decrease after the crossing, which corresponds to the sudden drop of diffusion coefficient at the SI. However, this effect is not observed for the second period, the decrease of GCR counts are simply caused by the enhancement of the diffusion coefficient after the SI crossing. Moreover, heliospheric current sheet (HCS) correlate with GCR counts well, the GCRs drift along the current sheet and then accumulate to a pileup structure, which is physically balanced between their diffusion and drift effects. Finally, based on the observation and Parker transport theory, we discuss the physical mechanism of the GCR variation for the crossings of SIs and HCS, and proposed that the interplay between drift and diffusion determines the GCR distribution and variation at a heliocentric distance of 1 AU. 19TH ANNUAL INTERNATIONAL ASTROPHYSICS CONFERENCE ORAL ABSTRACTS

Gurnett, Don Voyager 1 and 2 Radio and Plasma Wave Measurements and Their Role in Exploring the Heliopause and the Very Local Interstellar Plasma D. A. Gurnett, University of Iowa, USA W. S. Kurth, University of Iowa, USA As the Voyager 1 and 2 spacecraft traveled outward from the Sun after their launch in 1977, the plasma wave instruments on both spacecraft detected two unusual very intense radio emission events in the frequency from about 2 to 3 kHz, the first starting in August 1983 and the second starting in July 1992. The spacecraft at these times were well beyond the orbit of Saturn at radial distances ranging from about 13 to 51 AU (Astronomical Units). These events were eventually shown to have occurred about 400 days after the two strongest cosmic ray Forbush decreases ever observed, the first (a 21% decrease) starting in July 1982 and the second (a 30% decrease) starting in May 1991. Forbush decreases are known to be caused by large‐scale global shock waves and associated plasma disturbances propagating outward from the Sun in response to energetic solar events. The turbulent magnetic fields associated with these disturbances cause transient decreases in the cosmic ray intensities. Motivated by our understanding of type II and type IV solar radio emissions, we proposed that the 2 to 3 kHz radio emissions were produced by electron plasma oscillations excited when the strong 1982 and 1991 shocks reached and interacted with the interstellar plasma near and beyond the heliopause. From the shock velocities, which where estimated to range from 500 to 800 km/s, and the 400‐day travel time, the distance to the heliopause was estimated to be 116 to 177 AU. At this great distance from the Sun the interstellar plasma density was such that the plasma oscillation frequency, fp = 8980√ne Hz, where ne is the electron density, is consistent with the frequency of the 2 to 3 kHz radio emissions. Although it took nearly thirty years for the spacecraft to reach the source region of the 2 to 3 kHz radio emissions, the above model for the generation of the 2 to 3 kHz radio emission was confirmed in October 2012 when the Voyager 1 plasma wave instrument began detecting locally generated electron plasma oscillations at a frequency of 2.1 kHz and a radial distance of 122.6 AU. This oscillation frequency corresponded to an electron density of 0.055 cm(‐3), which was roughly the density expected from remote sensing and other estimates of the plasma density in the very local interstellar medium (VLISM). These observations confirmed that that the spacecraft had crossed the heliopause on or about August 25, 2012, at a heliocentric radial distance of 121.6 AU as suggested by the other Voyager 1 instruments. Subsequent measurements of plasma oscillations by Voyager 1 as it moved farther out into the interstellar medium have shown that the plasma density has increased to approximately 0.12 cm(‐3) in the most recent data at 146 AU, well above the very low solar plasma densities, ~0.002 cm(‐3). characteristic of the heliosheath. We call this region of increasing plasma density immediately beyond the heliopause the heliospheric boundary layer. It has a thickness on the order of 10 AU, or more. On November 5, 2018, Voyager 2 reached the heliopause at a heliocentric radial distance of 119.0 AU, and the first plasma oscillations observed by the plasma wave instrument gave a density of 0.039 cm(‐3) at 119.7 AU, very similar to those measured by Voyager 1 at 122.6 AU. It is not clear whether the most recent Voyager 1 plasma density measurement of 0.12 cm(‐3) at 146 AU represents the asymptotic density of the VLISM, or is near a peak and will eventually decrease as the spacecraft moves further outward through the heliospheric boundary layer. The upper frequency cutoff, ~2.5 kHz, of a component of the 2 to 3 kHz radio emission that is thought to be trapped in the low‐density cavity of the heliosphere suggests that the density of the VLISM may be slightly lower, ~0.07 to 0.08 cm(‐3). It remains to be seen whether Voyagers 1 and 2 will remain operational long enough to fully resolve the large‐scale structure of the heliospheric boundary layer. Habbal, Shadia Total Solar Eclipse Observations: A Treasure Trove from the Source and Acceleration Regions of the Solar Wind Shadia Habbal, IfA, USA Despite the proliferation of ground‐ and space‐based observations of the solar corona, there is a critical spatial span of a few solar radii starting from the solar surface, which continues to defy exploration. At present, total solar eclipse observations are still unsurpassable for tackling this task. Taking advantage of the unique diagnostic potential of the visible wavelength range, and the rare observing conditions afforded by totality, which far surpass the quality of ground‐ and/or space‐borne coronagraphs, we show in this talk how multi‐wavelength imaging and spectroscopic eclipse observations of the corona have yielded novel insights into the quiescent and dynamic plasma properties of the corona. These observations also establish the connectivity between explosive events, including jets, prominence eruptions and coronal mass ejections, and the ambient coronal structures. They also reveal a preponderance of instabilities and induced wave motions triggered by the ubiquitous dynamic behavior of prominences. This invited presentation will demonstrate how eclipse observations provide an invaluable link between the corona and in‐situ observations, including the more recent PSP measurements. 19TH ANNUAL INTERNATIONAL ASTROPHYSICS CONFERENCE ORAL ABSTRACTS

Ho, George Solar Wind Streams Interaction Regions Observed by Parker Solar Probe George C. Ho, JHU/APL, USA Robert C Allen, JHU/APL, USA David Lario, GSFC, USA D. Odstrcil, GSFC, USA L. K. Jian, GSFC, USA Several fast streams and stream interaction regions (SIRs) were observed by Parker Solar Probe (PSP) during its first orbit (2018 September ‐ 2019 January). During this time, several recurring SIRs were also seen at one astronomical unit (au) at both L1 (ACE and WIND) and the location of STEREO‐A. In this paper, we compare four fast streams observed by PSP at different radial distances during its first orbit. For three of these fast stream events, measurements from L1 (ACE and WIND) and STEREO‐A indicated that the fast streams were observed by both PSP and at least one of the 1 au monitors. Our associations are supported by simulations made by the ENLIL model using AGONG‐ ADAPT‐WSA which allows us to contextualize the inner heliospheric conditions during the first orbit of PSP. Additionally, we determine which of these fast streams are associated with an SIR and characterize the SIR properties for these events. From these comparisons we find that the compression region associated with the fast speed streams can form at various radial distances from the Sun in the inner heliosphere below 0.5 au, with the suprathermal ion population (energies between 30 – 586 keV) being observed as local enhancements in isolated regions near the SIR at ~0.3 au, unlike at 1 au where the suprathermal enhancement can last for over a day after the SIR interface is observed. This suprathermal enhancement is seen to extend further into the fast stream with increasing distance from the Sun. Hu, Junxiang Challenges and Recent Progress in SEP Modeling and Forecast Junxiang Hu, UAH/CSPAR, USA Gang Li, UAH/CSPAR, USA Frederic Effenberger, GFZ‐Potsdam, Germany Timo Laitinen, University of Central Lancashire, UK SEP (solar energetic particles) event is one of the most prominent types of hazards in the heliosphere. A practical and validated SEP prediction/forecast model has been highly sought‐after in the space weather community for a long time. However, complexities in the acceleration and transport process of the solar energetic particles make it a difficult task for model developers. In this study, we will discuss the outstanding challenges lying ahead for physics‐based SEP models, such as our lack of knowledge in turbulence evolution, suprathermal seed population, and diffusion mechanisms. We will present some of our recent efforts in reducing uncertainties in these aspects, with the help of advanced theoretical and observational results. We will also show the latest updates on our iPATH model and its potential for the SEP forecast. Intriligator, Devrie Heliosphere Configuration Insights from Voyagers’ Heliopause Crossings and Solar Disturbance Propagations Devrie Intriligator, Carmel Research Center, Inc., USA W. David Miller, Carmel Research Center, Inc., USA James Intriligator, Tufts University and Carmel Research Center, Inc., USA William Webber, New Mexico State University, USA (Deceased) The Voyager 1 and 2 (V1 and V2) observations from the heliopause (HP) have generated new estimates of the shape of the heliosphere, helped elucidate plasma wave features, and helped clarify distinctions in particle and field data all of which provide insights into the overall configuration of the heliosphere and its interaction with the local interstellar medium (LISM). Webber and Intriligator (2011) indicated the suggested offset in the V1 and V2 locations of the termination shock (TS) crossings, predicted a shrunken and squashed geometry of the heliosphere, and correctly predicted that V1 would encounter the HP in 2012.0 ± 1 year. Intriligator et al. (2005, 2008) examined solar events (i.e., space weather) that could disrupt the configuration of the heliosphere giving rise to Global Merged Interaction Regions and to broad particle and field offsets from the Halloween 2003 solar events manifest from the Sun to V1 and V2 at 92.6 and 73.2 AU. The 2012 solar events (Intriligator et al., 2015) appeared to cause a tsunami at V1 and V2 at 128.7 and 102.5 AU and emphasized space weather often could be interpreted as TS or HP or heliospheric crossings. Voyager plasma wave events (Gurnett and Kurth, 2020) indicate their propagation into the LISM. Washimi et al. (2017) suggested that further complications of these events could propagate from the LISM back into the heliosphere. We discuss the extent to which currently available information clears up some of these past uncertainties. 19TH ANNUAL INTERNATIONAL ASTROPHYSICS CONFERENCE ORAL ABSTRACTS

Jian, Lan Data Infrastructure Supporting the Heliophysics Research L. Jian, NASA GSFC, USA R. Candey, NASA GSFC, USA There is a fleet of NASA or NASA‐joint spacecraft missions observing the heliosphere from the Sun to the interstellar medium. The Solar Data Analysis Center (SDAC) and Space Physics Data Facility (SPDF) located at the NASA Goddard Space Flight Center are the Active Final Archives for remote‐sensing data of the Sun, and non‐solar or in‐situ data from heliophysics missions, respectively. The SPDF also archives and serves the non‐solar data from other missions or projects related to the heliophysics research. Furthermore, SPDF has been providing support for the Common Data Format (CDF) software, the Heliophysics Data Environment (HPDE) metadata guidelines, and the Space Physics Archive Search and Exact (SPASE) metadata. This talk will introduce the data infrastructure of SPDF and how to use it to facilitate the heliophysics research. Kahler, Stephen Energy Budgets of Coronal Mass Ejections and Flares in Connected Events Stephen Kahler, Air Force Research Laboratory, USA Alan Ling, AER, USA Maria Kazachenko, LASP, USA Solar eruptive events convert magnetic energy into two primary components. Kinetic energy is carried off by coronal mass ejections (CMEs) propagating into the heliosphere, and thermal energy is manifested by heated coronal plasma of solar flares. The way in which the magnetic energy is proportioned between the flare and CME components may be described by a regular scaling relationship for all events, or it may be primarily dependent on the magnetic configuration of the source region. In a recent work Kahler & Ling (2020) found that for a given X‐ray flare size (e.g,, GOES level M or X), cooler flares are statistically associated with faster CMEs, contrary to a simple energy proportionality between CMEs and flares. That work used an X‐ray proxy for flare temperature, did not involve flare or CME energies, and made no comparison to the reconnection magnetic energies. Here we use catalogs of X‐ray flare temperatures and emission measures (TEBBS), CME energies, and magnetic reconnection energies to test for possible scaling relationships and derive CME and flare energy budgets. Flare durations are also compared with their energies and sizes and properties of associated CMEs. Kilian, Patrick How Magnetic Reconnection Injects Particles and Accelerates them to High Energies Patrick Kilian, Los Alamos National Lab, USA Xiaocan Li, Dartmouth College, USA Fan Guo, Los Alamos National Lab, USA Hui Li, Los Alamos National Lab, USA Magnetic reconnection is a ubiquitous process, happening everywhere from solar flares over the magnetotail to astrophysical sources. It is able to convert magnetic field energy to kinetic energy in bulk motion, plasma heating as well as super‐thermal particles. This tail of energetic particles can form a power law and extends to high energies where it can be observed by its generated emission. To understand the formation of this particle population and its dependence on plasma parameters we study the underlying acceleration mechanisms that energize a fraction of the particles. We performed large kinetic particle‐in‐cell simulations of magnetic reconnection in the trans‐ relativistic regime using VPIC. We find that the injection process that picks particles out of the thermal distribution does not have to rely on the electric field parallel to the local magnetic field. Instead we find that the perpendicular electric field can accelerate particles directly through a Fermi‐like process. This process is also the dominant acceleration term at high particle energies. This is interesting because the parallel field is mostly produced by non‐ideal kinetic effects in the diffusion region directly around the reconnection X point and can be readily screened. The perpendicular field can be produced on much larger scales by fast plasma flows driven by relaxing field lines. This might explain why this process becomes more effective at large system sizes.

19TH ANNUAL INTERNATIONAL ASTROPHYSICS CONFERENCE ORAL ABSTRACTS

Kim, Tae Modeling the Time‐dependent Solar Wind, Interstellar Pickup Ions, and Turbulence at the Ulysses, Voyager, and New Horizons Spacecraft Using Empirically‐derived Boundary Conditions Tae K. Kim, The University of Alabama in Huntsville, USA Nikolai V. Pogorelov, The University of Alabama in Huntsville, USA Igor A. Kryukov, Russian Academy of Sciences, Russia Gary P. Zank, The University of Alabama in Huntsville, USA Heather A. Elliott, Southwest Research Institue, USA David J. McComas, Princeton University, USA Eric J. Zirnstein, Princeton University, USA The outer heliosphere is an interesting region characterized by the interaction between the solar wind and the interstellar neutral atoms. Having accomplished the mission to Pluto in 2015 and currently exploring the Kuiper Belt, the New Horizons (NH) spacecraft is gradually approaching the boundary of the heliosphere, trailing only the Voyager 1 and 2 spacecraft that have exited the heliosphere in 2012 and 2018, respectively. We model the three‐dimensional, time‐dependent solar wind plasma flow to the outer heliosphere using our own software Multi‐Scale Fluid‐Kinetic Simulation Suite (MS‐FLUKSS), which, in addition to the thermal solar wind plasma, takes into account charge exchange of the solar wind protons with interstellar neutral atoms and treats nonthermal ions (i.e., pickup ions) born during this process as a separate fluid. Additionally, MS‐ FLUKSS allows us to model the turbulence generated by pickup ions. We use MS‐FLUKSS to investigate the evolution of plasma and turbulent fluctuations along the trajectory of the New Horizons spacecraft using plasma and turbulence parameters from OMNI data as time‐dependent boundary conditions at 1 AU to solve the Reynolds‐averaged MHD equations. We compare the model with in situ plasma observations by NH, Voyager 2, and Ulysses. We also compare the model pickup proton parameters with those derived from the NH‐SWAP and Ulysses‐SWICS data. Klein, Kristopher The Distribution of Proton and Alpha‐driven Microinstabilities in the Inner Heliosphere K.G. Klein, UArizona, USA M. Martinovic, UArizona, USA D. Stansby, UCL, England T. Ďurovcová, Charles University, Czech Republic T. Horbury, Imperical, England The nearly‐collisionless nature of the low‐density, high‐temperature solar wind allows it to depart from local thermodynamic equilibrium (LTE). This departure drives unstable growth. Unstable wavemodes are frequently inferred from in situ observations of the solar wind. Understanding the nature of these instabilities is necessary to fully characterize how energy is transported and dissipated in the solar wind and similar systems. To do so, we must investigate how frequently they occur as a function of distance from the Sun and other characteristic parameters. Given the large number of non‐LTE structures that can drive these instabilities, e.g. temperature anisotropies, temperature disequilibrium between species, and relative drifts, we use an automated implementation of the Nyquist criterion instead of more traditional parametric models to determine the stability of a measured interval. This automated method had been used on solar wind observations at 1 au from the Wind spacecraft, finding that over half of the sampled intervals supported linearly growing modes. In this work, we apply the Nyquist criterion to tens of thousands of ion spectra measured by the Helios spacecraft in order to determine how frequently ion‐driven instabilities arise in the inner heliosphere, and how the characteristics of these instabilities change under the influence of key plasma and solar wind parameters. These results will be expanded upon using measurements from Parker Solar Probe, which has now gone closer to the Sun than any previous mission, to refine our understanding of the role wave‐particle instabilities play in shaping the evolution of the expanding solar wind. 19TH ANNUAL INTERNATIONAL ASTROPHYSICS CONFERENCE ORAL ABSTRACTS

Klimchuk, James The Onset and Development of 3D Magnetic Reconnection James A. Klimchuk, NASA‐GSFC, USA Lars Daldorff, Catholic U. of America, USA James E. Leake, NASA‐GSFC, USA Magnetic reconnection is a fundamentally important process that occurs throughout the heliosphere and beyond. It is responsible for coronal heating, solar flares, magnetospheric substorms, and other phenomena that involve the explosive release of magnetic energy. One of the most crucial properties of reconnection is its “switch on” nature. It must remain dormant to allow magnetic stresses to build to substantial levels and then suddenly activate. Were reconnection to occur too soon, the noted phenomena would be much weaker than observed. It is widely believed that reconnection is initiated by the tearing instability of an electric current sheet. We have performed a series of resistive MHD simulations and found that whether and how the tearing develops nonlinearly and releases substantial energy depends critically on the properties of the sheet, including its width, length, and degree of magnetic shear (amount of field rotation). We have identified three distinct evolutionary paths that can be predicted based on the relative growth rates of the different tearing modes in the earliest phase of linear evolution. Thus, small amplitude effects set the stage for what is to become. We discuss our results in the context of solar phenomena. Krimigis, In‐situ Hot Plasma Ion Measurements by Voyagers in Heliosheath and Galaxy, and Global ENA Images by Cassini/INCA: Pressures and Dynamics Stamatios S. M. Krimigis, JHU/APL, USA R. B. Decker, JHU/APL, USA K. Dialynas, Academy of Athens, Greece D. G. Mitchell, JHU/APL, USA J. H. Westlake, JHU/APL, USA E. C. Roelof, JHU/APL, USA Voyager 1 (V1) entered the heliosheath (HS) in December 2004 at 94 AU and crossed the heliopause (HP) in August 2012 at 121.6 AU, while Voyager 2 (V2) entered HS in August 2007 at 84 AU and exited the HP in November 2018 at 119 AU. The very similar crossing distances are remarkable in that V1's crossing of HP occurred at solar minimum while that of V2 near solar maximum. Thus, the properties of the HS along the V1, V2 trajectories are now well‐established (Krimigis et al., 2019). Portions of the global HS have been imaged by the Cassini/INCA (Ion and Neutral CAmera) since 2000 at E>5 keV, complemented since 2009 with those of IBEX at lower (<5 keV) energies. The presence of the two Voyagers measuring ions locally in the HS, contemporaneously with INCA global imaging through ENA in overlapping energy bands provides a powerful tool for examining the spatial, temporal, and spectral evolution of the source hot plasma ions and the global variability of the neutral component. Some of the key findings from the Voyagers and INCA measurements are as follows: (a) The HS contains a hot plasma population that carries a substantial part (40‐60 %) of the total pressure at E > 5 keV, the rest residing below that range, resulting in a beta (particle/magnetic pressure) always > 1, typically >10. (b) The width of the HS in the direction of V1 is ~ 27 AU, but is ~ 35 AU in the southern ecliptic traversed by V2. (c) The ENA intensities at E > 5 keV exhibit a correlation with the solar cycle (SC) over the period 2000 to 2016, with minimum intensities in the nose and anti‐nose direction observed ~ 2.5 years after solar minimum followed by a recovery thereafter in both directions, and (d) The in‐situ ion measurements at V2 within the HS also show a similar SC dependence, implying that the source of such emissions at E>5 keV is in the HS. The totality of these observations, together with the recent magnetic field measurements upstream of the HP from both V1 and V2, constrain the shape of the heliosphere and suggest a Parker rough "bubble" configuration rather than the heretofore assumed comet‐like tail of tens of thousands of AU (Krimigis et al, 2009; Dialynas et al. 2017, 2019). Krimigis et al, Science, 326, 971, 2009 Dialynas et al, Nature Astronomy, 1, 115, 2017 Dialynas et al, Geophys. Res. Letts., 46, 1, 2019 Krimigis et al, Nature Astronomy, 3, 997, 2019 19TH ANNUAL INTERNATIONAL ASTROPHYSICS CONFERENCE ORAL ABSTRACTS

Lario, David A Long‐Lasting Field‐Aligned Suprathermal Proton Beam Upstream of a Transient Interplanetary Shock D. Lario, NASA, Goddard Space Flight Center, USA L. Berger, Christian‐Albrechts‐Universitt zu Kiel, Germany L.B. Wilson III, NASA, Goddard Space Flight Center, USA R.B. Decker, The Johns Hopkins University, USA E.C. Roelof, The Johns Hopkins University, USA The properties of the suprathermal particle distributions observed during the passage of collisionless shocks in the interplanetary medium depend not only on the shock parameters but also on the transport conditions found by the particles as they propagate away from the shocks. Confinement of particles in the close proximity of the shocks as well as scattering processes undergone by the particles as they propagate to the spacecraft lead to the common observation of nearly isotropic particle distributions. We present here the unique observation of an extended anisotropic particle intensity increase observed in association with the arrival of an oblique interplanetary shock at the ACE and Wind spacecraft on day 31 of 2001. Continuous injection of particles by the traveling shock into a region characterized by radial smooth magnetic field produces an extended foreshock region of energetic particles. The absence of enhanced magnetic field fluctuations upstream of the shock results in the observation of an extended anisotropic field‐aligned beam of particles at both low (<~30 keV) and high (>~50 keV) energies that might reflect the distribution of particles escaping from the processes of particle acceleration at the shock. Le, Ari Wavelet Methods for Studying the Onset of Strong Plasma Turbulence Ari Le, LANL, USA Vadim Roytershteyn, Space Science Institute, USA Homa Karimabadi, Analytics Ventures, USA Adam Stanier, LANL, USA Luis Chacon, LANL, USA Kai Schneider, Institut de Mathematiques de Marseille, France Recent simulations have demonstrated that coherent current sheets dominate the kinetic‐scale energy dissipation in strong turbulence of magnetized plasma. Wavelet basis functions are a natural tool for analyzing turbulent flows containing localized coherent structures of different spatial scales. Here, wavelets are used to study the onset and subsequent transition to fully developed turbulence from a laminar state. Originally applied to neutral fluid turbulence, an iterative wavelet technique decomposes the field into coherent and incoherent contributions. In contrast to Fourier power spectra, finite time Lyapunov exponents, and simple measures of intermittency such as non‐Gaussian statistics of field increments, the wavelet technique is found to provide a quantitative measure for the onset of turbulence and to track the transition to fully developed turbulence. The wavelet method makes no assumptions about the structure of the coherent current sheets or the underlying plasma model. Temporal evolution of the coherent and incoherent wavelet fluctuations is found to be highly correlated (a Pearson correlation coefficient of >0.9) with the magnetic field energy and plasma thermal energy, respectively. The onset of turbulence is identified with the rapid growth of a background of incoherent fluctuations spreading across a range of scales and a corresponding drop in the coherent components. This is suggestive of the interpretation of the coherent and incoherent wavelet fluctuations as measures of coherent structures (e.g., current sheets) and dissipation, respectively. The ratio of the incoherent to coherent fluctuations is found to be fairly uniform in the turbulent state across different plasma models and provides an empirical threshold of ∼0.1 for turbulence onset. The utility of this technique is illustrated through examples. First, it is applied to the Kelvin–Helmholtz instability from different simulation models including fully kinetic, hybrid (kinetic ion/fluid electron), and Hall MHD simulations. Second, the wavelet diagnostic is applied to the development of turbulence downstream of the bowshock in a global magnetosphere simulation. 19TH ANNUAL INTERNATIONAL ASTROPHYSICS CONFERENCE ORAL ABSTRACTS le Roux, Jakobus Modeling Energetic Particle Acceleration and Transport in a Solar Wind Region with Dynamic Small‐Scale Flux Ropes at 1 AU Jakobus le Roux, University of Alabama in Huntsville, USA Gary Webb, University of Alabama in Huntsville, USA Olga Khabarova, IZMIRAN, Russia Ongoing observations in the inner heliosphere suggest that dynamic small‐scale magnetic flux‐ropes (SMFRs) occur much more commonly in the solar wind than previously thought, especially near reconnecting large‐scale current sheets. Furthermore, enhanced energetic particle fluxes are often observed to coincide with regions of active SMFRs, suggesting efficient energetic particle acceleration by these structures. To model the observed energetic particle acceleration in such SMFR regions in the large‐scale solar wind, a focused transport based Fokker‐Planck equation was developed before. In this presentation, new analytical solutions of the acceleration of energetic particles by SMFRs on large scales in the solar wind will be presented. For this purpose a telegrapher‐type Parker transport equation was derived from the underlying Fokker‐Plank equation that unify all SMFR acceleration mechanisms present in the transport theory. We will discuss the potential of these solutions in reproducing energetic proton flux enhancements and spectral evolution between ~50 keV ‐ 5 MeV in dynamic SMFR regions near large‐scale reconnecting current sheets in the solar wind at Earth orbit. Both 1st and 2nd order Fermi SMFR acceleration mechanisms were evaluated by specifying reasonable SMFR parameters. The results show significant differences in the spatial evolution of the accelerated spectra through the SMFR region that might provide a way to distinguish between 1st and 2nd order Fermi SMFR acceleration in observations. Lembege, Full Particle Simulations of Energy Spectra Measured by SWAP Experiment (New Horizon Mission) around an Interplanetary Shock near PLuto: a Parametric Analysis Bertrand Bertrand Lembege, LATMOS‐CNRS‐UVSQ‐IPSL, France Zhongwei, Yang, IGG, CAS, China Very detailed energy spectra of solar wind and pickup ions (PUIs) have been observed by New Horizon’s mission at a distance between 25 to 38 A.U. , thanks to the SWAP (Solar Wind Around Pluto) experiment (Mc Comas et al., 2017). Moreover, similar spectra have been observed in the upstream region of an interplanetary shock during the flyby of Pluto at a distance of 34 A.U. (Zirnstein et al., 2018). Recent 1D PIC simulations (Lembege et al., 2020) have been performed including different solar wind ion (SWIs) and pick up ion (PUIs) populations, namely, SWI‐H+, SWI‐He++, and PUI‐H+, and PUI‐He+, where H+ and (He+ and He++) note protons and helium ions respectively, approaching the experimental conditions observed by SWAP experiment. This approach has allowed to determine the role of the each population within different energy ranges, and to confirm that the high energy range of the spectrum is mainly carried by backstreaming (BS) PUIs which, after interacting with the shock front, are reflected and reinjected back far into the upstream region. The present work is an extension of this previous analysis : (A) different critical angular ranges have been identified namely (90° > Θ > ΘPUIs) where no BS‐ions appear, (ΘPUIs > Θ > ΘSWIs) where only BS‐PUIs appear, and (ΘSWIs > Θ) where both BS‐PUIs and BS‐SWIs appear; (B) in range (ΘPUIs > Θ > ΘSWIs) a strong upstream wave activity has been identified as due to the interaction between incoming/backstreaming PUIs only, which impact the dynamics of electrons and of incoming SWIs ; (C) these different dynamics also impact the respective contribution of SWIs and PUIs in the global energy partition, and their associated energy spectra. Simulation results will be presented and compared with local SWAP experimental results. 19TH ANNUAL INTERNATIONAL ASTROPHYSICS CONFERENCE ORAL ABSTRACTS

Leske, Richard Anomalous and Galactic Cosmic Ray Intensity Variations at 1 AU Throughout Two Complete Solar Cycles R. A. Leske, California Institute of Technology, USA A. C. Cummings, California Institute of Technology, USA R. A. Mewaldt, California Institute of Technology, USA E. C. Stone, California Institute of Technology, USA C. M. S. Cohen, California Institute of Technology, USA M. E. Wiedenbeck, Jet Propulsion Laboratory, California Institute of Technology, USA Both anomalous cosmic rays (ACRs) and galactic cosmic rays (GCRs) probe energetic particle transport conditions throughout the heliosphere. Long‐term measurements, including observations over two complete solar cycles from the Advanced Composition Explorer (ACE), have shown that modulated ACR and GCR intensities at 1 AU track each other, but exhibit differences between solar polarity cycles: at high rigidities, GCRs reach higher peak intensities during A<0 cycles, while ACRs are higher at A>0 solar minima. Comparing intensities in the same polarity cycles, we find that ACR oxygen intensities above ~8 MeV/nucleon in the present A>0 solar minimum as measured by the Solar Isotope Spectrometer (SIS) on ACE remain ~30% below the levels seen during the last A>0 minimum in 1997, while GCR iron intensities at ~300 MeV/nucleon from the Cosmic Ray Isotope Spectrometer (CRIS) exceed those in 1997 by ~20%. Similarly, in the 2009 A<0 minimum, peak ACR intensities were similar to those in the 1987 A<0 cycle, but GCR intensities reached record‐setting levels. The GCR observations indicate that there has been a decrease in heliospheric modulation during recent solar minima, but apparently ACR intensities at 1 AU have been reduced relative to GCRs. ACR intensities depend not only on solar modulation, but also on their source strength, which might be expected to vary with changes in the heliosphere. Contributing factors may include a reduction in the acceleration efficiency of ACRs due to a decrease in the strength or turbulence levels of the interplanetary magnetic field, or a drop in the abundance of ACR seed particles (pick‐up ions) due to less ionization in this epoch of weaker solar activity. We present more than 22 years of ACR and GCR intensities measured by ACE throughout two complete solar cycles and discuss possible reasons for the differences in the behavior of ACRs relative to GCRs in the recent solar cycles. Li, Hui 3D Turbulence with Global Reconnection Hui Li, LANL, USA Liping Yang, NSSC, China Xiaocan Li, Dartmouth College, USA Fan Guo, LANL, USA We present 3D MHD and kinetic simulations to study the interplay between turbulence and the pre‐existing current sheets. These systems are large enough that turbulence can be fully developed. The pre‐existing current sheets represent a source of available “free energy” that can be released and produce turbulence. We characterize the properties of the self‐generated turbulence and its impact on particles. We will discuss the implications for solar and accretion disk corona and astrophysical jets. Li, Hui Plasma‐Beta Modulated Characteristics of MHD waves around Heliospheric Current Sheet Hui Li National Space Science Center, CAS, China Nianwang Li National Space Science Center, CAS, China Chi Wang National Space Science Center, CAS, China Shuo Yao China University of Geosciences, China The magnetohydrodynamics (MHD) wave modes in the Heliospheric Current Sheet (HCS) and the associated Heliospheric Plasma Sheet (HPS) have not been comprehensively investigated in the literature. Based on a frequency‐related identification approach, the properties of MHD waves are investigated during 154 HCS crossings observed by the Wind spacecraft from 1995 to 2013. Statistically, the incidence of MHD waves around HCS/HPS is found to be modulated by the plasma beta within the HPS: 1) beta > 5, both Alfven and slow waves obviously decay within the HPS, with the occurrence rate (OR) decreasing from 60% and 20% in the upstream/downstream to 41% and 14% in the HPS vicinity, respectively; 2) 1 < beta ≤ 5, the OR of Alfven waves remains nearly stable. However, more slow waves are generated after the HCS crossing, with OR increasing from 13% in the upstream/downstream to 22%; 3) beta ≤ 1, the OR of Alfven and slow waves remains at 58% and 20% during the entire crossing, in spite of some irregular fluctuations. The results for the HCS without a clear HPS are similar to the situations of a low beta HPS. The parametric decay instability (PDI) of Alfven wave is suggested to be responsible for the more slow waves generated in the moderate beta HPS, and some indirect observational clues are also given. 19TH ANNUAL INTERNATIONAL ASTROPHYSICS CONFERENCE ORAL ABSTRACTS

Li, Xiaocan Particle acceleration and turbulence in 3D low‐beta magnetic reconnection Xiaocan Li, Dartmouth College, USA Fan Guo, Los Alamos National Laboratory, USA Hui Li, Los Alamos National Laboratory, USA Patrick Kilian, Los Alamos National Laboratory, USA Adam Stanier, Los Alamos National Laboratory, USA Magnetic reconnection is a primary driver of particle acceleration processes in space and astrophysical plasmas. One of the major unsolved problems in reconnection studies is nonthermal particle acceleration. Here we present results from 3D PIC simulations of low‐beta magnetic reconnection. We find that a clear power‐law energy spectrum can form and persist throughout the 3D simulations. We show that 3D effects such as self‐generated turbulence and chaotic magnetic field lines enable the transport of high‐ energy electrons across the reconnection layer and allow them to access several main acceleration regions. This leads to a sustained and nearly constant acceleration rate for electrons at different energies. We will present the results from simulations with different guide field and discuss the properties of the self‐generated turbulence in 3D reconnection (e.g. spectrum and anisotropy). These results are important for understanding particle acceleration during magnetic reconnection in solar corona and near‐Sun solar wind. Liang, Haoming Kinetic Entropy as a Diagnostic in Particle‐in‐Cell Simulations of Astrophysical, Heliospheric, and Planetary Plasmas Paul Cassak, West Virginia University, USA Sergio Servidio, Università della Calabria, Italy Oreste Pezzi, Gran Sasso Science Institute, Italy Mahmud Barbhuiya, West Virginia University, USA Michael Shay, University of Delaware, USA James Drake, University of Maryland, USA Marc Swisdak, University of Maryland, USA Matt Argall, University of New Hampshire, USA John Dorelli, NASA‐Goddard Space Flight Center, USA Earl Scime, West Virginia University, USA William Matthaeus, University of Delaware, USA Vadim Roytershteyn, Space Science Institute, USA Gian Luca Delzanno, Los Alamos National Laboratory, USA Kinetic entropy is the entropy defined using kinetic theory for plasmas that are not necessarily in local thermodynamic equilibrium. Entropy is a natural metric of irreversible dissipation since it is conserved in ideal isolated systems and increases only when there is dissipation. This suggests kinetic entropy can address important unsolved questions on the nature of irreversible dissipation in fundamental plasma processes such as magnetic reconnection, plasma turbulence and collisionless shocks in heliospheric, planetary, and astrophysical systems. While entropy is often investigated in fluid and gyrokinetic systems, it is vastly underutilized in fully kinetic systems. In this work, we carry out an initial study to develop and apply the kinetic entropy diagnostic in particle‐in‐cell (PIC) simulations. As an example, we setup simulations of 2.5D collisionless anti‐parallel reconnection and calculate the commonly‐used kinetic entropy written as the phase space integral of – f ln f, where f is the distribution function, and the full Boltzmann entropy related to the logarithm of the number of microstates for a specific macrostate. We find that total kinetic entropy in the simulations is preserved quite well (better than three percent) and the departure from exact conservation can be used to quantify the effective numerical dissipation. By decomposing kinetic entropy into a sum of velocity space and position space entropies, we show that position space entropy decreases while velocity space entropy increases during magnetic reconnection. Electrons and ions have slightly different effective collision frequencies. We finally use kinetic entropy to identify regions with non‐Maxwellian distributions and compare with Magnetospheric Multiscale (MMS) data as well as the results with other approaches. Note that we cannot yet address physical dissipation mechanisms in current study based on collisionless simulations; nonetheless, the infrastructure developed here will be useful for future studies in weakly collisional systems. Current applications of this diagnostic to reconnection with different plasma betas and weakly collisional turbulence are shown. 19TH ANNUAL INTERNATIONAL ASTROPHYSICS CONFERENCE ORAL ABSTRACTS

Linsky, Jeffrey New Results Concerning the Environment of the Heliosphere, Nearby Interstellar Clouds, and Physical Processes in the Intercloud Medium Jeffrey L. Linsky, University of Colorado, USA Seth Redfield, Wesleyan University, USA We will provide new results concerning the interface between the outer heliosphere and the local interstellar medium. The three dimensional shape of the Local Interstellar cloud (LIC) based on 62 sightlines to nearby stars shows a region of very low neutral hydrogen column density in the direction of the star Epsilon CMa, the brightest source of extreme‐UV radiation. This "hydrogen hole" with no detected absorption by the LIC and weak absorption by the Blue cloud indicates photionization from the EUV radiation of Epsilon CMa. The LIC likely surrounds the heliosphere, but in the direction of the hydrogen hole its column density is too low to be measured. Upper limits to this column density and the direction of the Sun's motion through space predict that the Sun will leave the outer edge of the LIC in less than 1900 years. The measured difference between the speed and direction of incoming neutral helium atoms (IBEX and Ulysses) and the flow vector of the LIC indicate that the plasma at the edge of the LIC has a different flow vector than the LIC core. The Blue, Aql, and G clouds of partially ionized interstellar plasma are very close to the heliosphere and at least another 10 clouds are located within 10 pc of the Sun. The intercloud plasma and much of the Local Bubble are part of the Stromgren sphere (also called an H II region) surrounding Epsilon CMa. The outer edges of the LIC and other clouds are Stromgren shells that are partially ionized by the EUV radiation primarily from Epsilon CMa but also from other hot stars and white dwarfs. When the Sun leaves the LIC it will likely enter the G cloud or its Stromgren shell. Livadiotis, George H‐theorem and Entropy Associated with Kappa Distributions; Application in Solar Wind Plasma George Livadiotis, Southwest Research Institute, USA Recently, we have shown the following fundamental properties of kappa distributions: (i) the theoretical framework of kappa distributions can be naturally derived from only the thermodynamic laws; (ii) one‐to‐one connection of kappa distributions with the polytropic behavior; (iii) invariance of kappa distribution formulation, that is, independence of dimensionality, degrees of freedom, or number of particles; and (iv) Rankine‐Hugoniot conditions for shocks in plasmas described by kappa distributions. These properties constitute the basic keys for understanding the Landau kinetic equations, the H‐theorem, and the entropy evolution, associated with kappa distributions. As an example, the entropy radial evolution along the heliosphere is determined and discussed. Mackey, Jonathan Magnetised Wind Bubbles around Massive Stars Jonathan Mackey, Dublin Institute for Advanced Studies, Ireland Samuel Green, Dublin Institute for Advanced Studies and University College Dublin, Ireland Maria Moutzouri, Dublin Institute for Advanced Studies and University College Dublin, Ireland Thomas J. Haworth, Queen Mary University of London, UK Vasilii V. Gvaramadze, Lomonosov Moscow State University and Russian Academy of Sciences, Russia Hot massive stars of spectral type O, B and Wolf‐Rayet have atmospheres and winds consisting of ionized plasma, probably weakly magnetised, streaming out at speeds of 1000‐5000 km/s. Some have detectable large‐scale magnetic fields of 300‐10,000 G at the surface, but about 90 per cent have only upper limits on the magnetic field. Stellar rotation winds up the magnetic field just like in the Solar Wind. I will describe 3D magnetohydrodynamic (MHD) simulations of wind bubbles (astrospheres) for O stars moving through interstellar space, discussing similarities with, and differences from, the Heliosphere. For the bow‐shock around the O star Zeta Ophiuchi, we use the simulations to refine previous observational estimates of the wind strength. Comparing simulations with observations of diffuse thermal X‐ray emission from the shocked stellar wind, we find good agreement in one case but disagreement in another. This has implications for the energetics of wind bubbles, especially heat dissipation at the astropause mediated by hydrodynamic mixing and/or non‐ideal MHD processes. Observations of radio synchrotron radiation from bow shocks around massive stars reveal particle acceleration in astrospheres, and can potentially be used to constrain stellar magnetic field strengths. I will discuss our preliminary work in this area. 19TH ANNUAL INTERNATIONAL ASTROPHYSICS CONFERENCE ORAL ABSTRACTS

Martinović, Proton Stochastic Heating Becomes Increasingly Important in the near‐Sun Solar Wind Mihailo Mihailo M. Martinović, University of Arizona, USA Kristopher G. Klein, University of Arizona, USA Justin C. Kasper, University of Michigan, USA Anthony W. Case, Smithsonian Astrophysical Observatory, USA Kelly E. Korreck, Smithsonian Astrophysical Observatory, USA Davin Larson, University of California, Berkeley, USA Roberto Livi, University of California, Berkeley, USA Michael Stevens, Smithsonian Astrophysical Observatory, USA Phyllis Whittlesey, University of California, Berkeley, USA Benjamin D. G. Chandran, University of New Hampshire, USA Ben L. Alterman, Southwest Research Insitute, USA Jia Huang, University of Michigan, USA Christopher H. K. Chen, Queen Mary University of London, UK Stuart D. Bale, University of California, Berkeley, USA Marc Pulupa, University of California, Berkeley, USA David Malaspina, University of Colorado, USA John W. Bonnell, University of California, Berkeley, USA Peter R. Harvey, University of California, Berkeley, USA Keith Goetz, University of Minnesota, USA Thierry Dudok de Wit, LPC2E, CNRS and University of Orleans, France Robert J. MacDowall, NASA/Goddard Space Flight Center, USA

Stochastic heating is a non‐linear heating mechanism driven by the violation of magnetic moment invariance due to large‐amplitude turbulent fluctuations. The solar wind heating by this mechanism in the direction perpendicular to the magnetic field is achieved through diffusion of ions towards higher kinetic energies. Here, we quantify the proton stochastic heating rate as close as 0.16 au from the Sun, using measurements from the first two Parker Solar Probe encounters. Our results for both the amplitude and radial trend of the heating rate agree with previous results based on the Helios data set at heliocentric distances from 0.3 to 0.9 au. Stochastic heating rate is significantly larger in the fast solar wind than in the slow solar wind. We identify the tendency in fast solar wind for cuts of the core proton velocity distribution transverse to the magnetic field to exhibit a flat‐top shape. The observed distribution agrees with previous theoretical predictions for fast solar wind where stochastic heating is the dominant heating mechanism. Matsukiyo, Heavy Ion Acceleration by Super‐Alfvenic Waves Shuichi S. Matsukiyo, Kyushu University, JPN T. Akamizu, Kyushu University, JPN T. Hada, Kyushu University, JPN A generation mechanism of super‐Alfvenic (SPA) waves in multi‐ion species plasma is proposed, and the associated heavy ion acceleration process is discussed. The SPA waves are thought to play important roles in particle acceleration since they have large wave electric fields because of their high phase velocity. It is demonstrated by using full particle‐in‐cell simulation that large amplitude proton cyclotron waves, excited due to strong proton temperature anisotropy, nonlinearly destabilize SPA waves through parametric decay instability in a three component plasma composed of electrons, protons, and alpha particles. At the same time, alpha cyclotron waves get excited via another decay instability. A pre‐accelerated alpha particle resonates simultaneously with the two daughter waves, the SPA waves and the alpha cyclotron waves, and it is further accelerated perpendicular to the ambient magnetic field. The process may work in astrophysical environments where a sufficiently large temperature anisotropy of lower mass ions occurs. 19TH ANNUAL INTERNATIONAL ASTROPHYSICS CONFERENCE ORAL ABSTRACTS

Mazelle, Christian Influence of Impact Ionization by Foreshock Electrons on the Amplitude of Pickup Protons Generated Waves Karim Meziane, University of New Brunswick, Canada N. Romanelli, NASA/GSFC, USA David L. Mitchell, UC Berkeley/SSL, USA Variations of the amplitude of electromagnetic waves at the local proton cyclotron frequency are observed by MAVEN upstream from the Martian bow shock on short (plasma) time/length‐scales: 1) a sharp sudden increase of the amplitude when crossing the electron foreshock boundary and 2) a decrease of this amplitude clearly correlated with the increasing distance from the shock along the magnetic field inside the foreshock without any simple relation to the planetary radial distance. These waves are excited by unstable ring‐beam velocity distributions of newborn protons produced by ionization of exospheric hydrogen atoms. The amplitude of these waves is generally expected to depend only on different drivers including the observed large seasonality of the hydrogen exosphere, the EUV solar flux, the solar wind density and velocity or the IMF cone angle at different levels of importance. No noticeable wave amplitude change is expected when crossing the electron foreshock boundary and inside the pure electron foreshock. Surprisingly, we found that that these waves also display the two same aforementioned properties as the foreshock electrons fluxes at Mars though the wave origin is related to the ions only. We investigate the possibility that the extra free energy necessary to increase the wave amplitude could be due to supplementary ionization of hydrogen atoms by electron impact ionization inside the foreshock. Therefore, the electron foreshock also plays a role in the production of pickup protons. McComas, David Imaging the Heliospheric Interaction over a Solar Cycle of Observations by the Interstellar Boundary Explorer (IBEX) Professor David McComas, Princeton University, USA The Interstellar Boundary Explorer (IBEX) was launched in 2008 and has now returned observations over a full 11‐year solar cycle (Solar Cycle 24). IBEX remotely images global ion distributions via charge exchange Energetic Neutral Atoms (ENAs) propagating inward from the heliosheath – the region between the termination shock and heliopause – and beyond. These observations have led to numerous discoveries about the outer heliosphere and its interaction with the surrounding interstellar medium. Heliospheric ENAs arise largely from two sources: the IBEX Ribbon, which is likely generated beyond the heliopause, in the very local interstellar medium, and the globally distributed flux (GDF), which is primarily produced in the heliosheath. In this talk we summarize some of the critical advances driven by IBEX observations. We also examine how the heliosphere and its interstellar interaction have evolved over the past solar cycle. For the first seven years of IBEX observations, there was an overall reduction and then flattening of the ENA fluxes at all energies, consistent with a generally “deflating” heliosphere. Over the past few years, however, IBEX has been observing the progressive response of the heliosphere to a large persistent increase in the solar wind output that passed 1 AU in the second half of 2014. This enhancement arrived at the outer heliosphere as indicated by an increase in the ENAs returning from the closest region of the inner heliosheath, south of the upwind direction, starting in the second half of 2016. Since then, the region of enhanced ENA emissions has expanded from there, exposing increasingly further away regions of the heliosheath. IBEX observations have led to a true scientific revolution in our understanding of the outer heliosphere and its interstellar interaction. 19TH ANNUAL INTERNATIONAL ASTROPHYSICS CONFERENCE ORAL ABSTRACTS

McNutt, Ralph Next Steps Past the Voyagers: A Pragmatic Interstellar Probe Ralph L. McNutt, Jr., Johns Hopkins University Applied Physics Laboratory, USA Robert F. Wimmer‐Schweingruber, Christian‐Albrechts‐Universität zu Kiel, Germany Mike Gruntman, University of Southern California, USA Stamatios M. Krimigis, Johns Hopkins University Applied Physics Laboratory, USA Edmond C. Roelof, Johns Hopkins University Applied Physics Laboratory, USA Pontus C. Brandt, Johns Hopkins University Applied Physics Laboratory, USA Kathleen E. Mandt, Johns Hopkins University Applied Physics Laboratory, USA Steven R. Vernon, Johns Hopkins University Applied Physics Laboratory, USA Michael V. Paul, Johns Hopkins University Applied Physics Laboratory, USA Robert W. Stough, NASA Marshall Space Flight Center, USA James D. Kinnison, Johns Hopkins University Applied Physics Laboratory, USA An “Interstellar Probe” to the nearby interstellar medium has been has been advocated by the science community for 60 years. The key concept has always been to depart from the Sun outward “as fast as possible.” Scientific goals have principally focused on heliospheric topics throughout multiple studies, with potential “bonus science” in both astrophysics and planetary science also discussed. Rather than “solving” the outstanding question of the interaction of the solar wind with the nearby interstellar medium, the passages of Voyagers 1 and 2 into that medium have only raised multiple new questions, e.g., to what extent does solar activity continue to have an effect on nearby interstellar space, why does the magnetic field change in magnitude and not direction across the heliopause, and what is the three‐dimensional structure of the energetic neutral atom (ENA) “ribbon.” The limited and decaying power levels on the Voyagers and noise “floors” of the payload limit the extent of our inquiries into these and other fundamental questions about our astrosphere’s interaction with the galaxy. The salient question for a dedicated interstellar probe mission is “What can the Interstellar Probe do that no other mission can do?” The answer is to “see” both in situ and remotely from an observation location otherwise not possible. The central technical question thus has always centered on propulsion: how does one reach a “large” distance from the Sun in a “timely” manner, and, indeed, what constitute “large” and “timely”? “Near‐ future” capabilities have always been the backdrop for defining engineering requirements but have also proven to date to be overly optimistic, leading to a repeating cycle of postponements followed by new studies. The real issue in breaking this cycle is the union of compelling science with engineering and technical reality at the present. To provide input to the upcoming Solar and Space Physics Decadal Survey, NASA’s Heliophysics Division has funded the Johns Hopkins University Applied Physics Laboratory (APL) to consider in depth a near‐term, “pragmatic” Interstellar Probe mission. The study has as its charge (1) to engage the broad science and technical communities, focused on heliophysics, but also including potential planetary and astrophysics goals, (2) assemble a “Menu” of what science could be accomplished on a mission launched in the time frame of the next Decadal, and (3) determine how that mission could be accomplished. Broad engineering requirements frame the study, focusing upon, but not limited to, the topics of (1) readiness, (2) downlink, (3) power, and, (4) longevity. Critical trade‐offs include mass versus flyout speed and downlink rate versus communications system, while enabling technologies of radioisotope power systems (RPS) and large launch vehicles are consistent with earlier studies. For moderate‐mass spacecraft, near‐term trades support the use of the Space Launch System (SLS) Block 2 configuration with existing or near‐term kick stages and a Jupiter gravity assist. An “advanced” concept using a near‐ Sun (“Oberth”) maneuver is also being investigated by building from Parker Solar Probe thermal shield technology. We provide a progress report on this ongoing effort. Medvedev, On Strong‐field QED Plasma in Magnetars Mikhail Mikhail Medvedev, KU & MIT, USA Quantum electrodynamics (QED) effects are interesting phenomena that occur in strong electromagnetic fields. Astrophysical systems such as strongly magnetized neutrons stars ‐‐ magnetars ‐‐ possess magnetic fields close to or even stronger than the Schwinger field. Whereas some QED effects are being understood and incorporated in plasma codes, theoretical studies of QED plasmas are lacking. Here we derive the general equations describing QED plasma modes. We discuss the properties of the low‐frequency modes, for which the transitions between the Landau levels can be neglected. These results can be of interest for understanding of the origin of fast radio bursts (FRBs). Supported by DOE via grant DE‐SC0016368, EPSCOR grant DE‐SC0019474 and by KITP via NSF grant PHY‐1748958. MM thanks the Razumovsky Moscow State University, NRC Kurchatov Institute and Moscow Institute of Physics and Technology. 19TH ANNUAL INTERNATIONAL ASTROPHYSICS CONFERENCE ORAL ABSTRACTS

Nakanotani, The Interaction of Current Sheets with a Shock Wave and Particle Acceleration Masaru Masaru Nakanotani, University of Alabama in Huntsville, USA Gary P. Zank, University of Alabama in Huntsville, USA L.‐L. Zhao, University of Alabama in Huntsville, USA The heliospheric current sheet (HCS) has a wavy structure that resembles a ballerina skirt due to the rotation of the Sun. The structure extends far away from the Sun and interacts with the heliospheric termination shock (HTS). The HTS has been considered as an accelerator for anomalous cosmic rays (ACRs). Voyager 1 & 2 observed the intensity of ACRs gradually increasing after crossing the HTS which was not expected. One explanation proposed by Zank et al. 2015 incorporates diffusive particle acceleration at a shock wave and particle acceleration by multiple magnetic reconnection events downstream simultaneously. The gradual increase in energetic particle intensity results from particle acceleration due to the magnetic island anti‐reconnection electric field and magnetic island contraction downstream. Reconnection downstream can be generated because of the interaction between the HCS and HTS. We study the interaction using 2D hybrid simulation in which electrons and ions are treated as a fluid and particles, respectively. A shock wave is formed by the injection method. We introduce multiple current sheets upstream perpendicular to the plasma flow satisfying the force‐free condition. While the current sheets are stable in the upstream flow, after crossing the shock wave they are compressed and become unstable and initiate extensive multiple and highly dynamical magnetic reconnection events. As a result, the electromagnetic fields become highly turbulent downstream. The downstream proton energy spectrum shows heated thermal plasma and non‐thermal particles, which exhibit a power‐law with an index of ‐3. Zhao et al. 2019 finds evidence of magnetic flux ropes downstream of the heliospheric termination shock and evidence of related particle acceleration. We report on the evolution of the current sheets downstream and the related particle acceleration. Opher, Merav The Structure of the Heliotail as probed by a Kinetic‐MHD, a Multi‐Ion Description of the Heliosphere and Energetic Neutral Maps Merav Opher, Adam Michael, Marc Zachary Kornbleuth, James Frederick Drake, Abraham Loeb and Gabor Toth A critical question regarding the heliosphere is its veryshape and the structure of the heliotail (whether it has a long comet‐like shape, is bubble shaped, or “croissant”‐like), prompted by observations and modeling (Opher et al. 2015; Pogorelov et al. 2015; Izmodenov & Alexashov 2015; Dialynas et al. 2017; Schwadron & Bzowski 2018). Opher et al. (2015) show that the magnetic tension of the solar magnetic field organizes the solar wind in the heliosheath into two jet‐like structures, giving the heliosphere a “croissant”‐ like shape where the distance to the heliopause downtail is almost the same as that towards the nose. There have been arguments that with a kinetic treatment of the neutral H, the heliotail extends to large distances (Izmodenov et al. 2018; Pogorelov et al. 2015). We recently developed the Solar‐ wind with Hydrogen Ion Exchange and Large‐scale Dynamics (SHIELD) model, a self‐consistent kinetic‐MHD model of the outer heliosphere within the SWMF framework (Toth et al. 2012). The SHIELD model couples the MHD solution for a single plasma buid to the kinetic solution for neutral hydrogen atoms streaming through the system. Our results show that even when the neutral H atoms are treated kinetically, the two‐lobe structure remains (Michael et al. 2019). Their results indicate that magnetic reconnection downtail and/or instabilities play a crucial role in the formation of the two‐lobe structure. We will present globally distributed flux (GDF) ENA maps from the SHIELD model, including a latitudinal variation of the solar wind corresponding to the conditions in the year 2008 using solar wind data from Sokol et al. (2015). The GDF ENA maps replicate the IBEX observations for solar minima conditions. We have also recently extended our global MHD model (Opher et al. 2020) to treat the pick‐up ions (PUIs) created in the supersonic solar wind as a separate buid from the thermal component of the solar wind. The PUIs charge exchange with the cold neutral H atoms of the ISM in the heliosheath and are quickly depleted. The depletion of PUIs cools the heliosphere downstream of the TS, “debating” it and leading to a narrower HS and a smaller and rounder shape. With this model, we reproduce the IBEX ENA observations along Voyager 2, as well the magnetic field observations at Voyager 1 and 2 ahead of the heliosphere. 19TH ANNUAL INTERNATIONAL ASTROPHYSICS CONFERENCE ORAL ABSTRACTS

Phan, Tai Parker Solar Probe In‐Situ Observations of Magnetic Reconnection in the Near‐Sun Environment Tai Phan, UC Berkeley, USA Stuart Bale, UC Berkeley, USA Jonathan Eastwood, Imperial College, UK Benoit Lavraud, IREP, France James Drake, U of Maryland, USA Marit Oieroset, UC Berkeley, USA Marc Pulupa, UC Berkeley, USA Michael Stevens, SAO, USA and the PSP FIELDS and SWEAP teams Magnetic reconnection in current sheets converts magnetic energy into particle energy. It has been suggested that reconnection may therefore play an important role in the acceleration and heating of the solar wind close to the Sun. Observations from Parker Solar Probe (PSP) provide a new opportunity to study this problem, as it measures the solar wind in situ at unprecedented distances to the Sun. During the first three orbits, PSP encountered a large number of current sheets in the solar wind through perihelion at 35.7 solar radii. Clear evidence for reconnection exhausts has been found in current sheets associated with Heliospheric current sheets, coronal mass ejections, small flux ropes, and the regular solar wind. However, we find that the majority of the current sheets encountered around perihelion, where the magnetic field is strongest and plasma beta lowest, were mostly Alfvenic structures associated with switchbacks. Although it has been suggested that these Alfvenic structures may be driven by reconnection lower in the corona, the majority of these current sheets do not appear to be undergoing local reconnection. We will discuss why some current sheets reconnect, while others do not. The PSP findings could help reveal the key conditions that control the presence or absence of reconnection in current sheets. Pierrard, Viviane Characteristics of the Suprathermal Population of Electrons in the Solar Wind Plasma Viviane Pierrard, Royal Belgian Institute for Space Aeronomy, Belgium Marian Lazar, KULeuven, Belgium Velocity distribution functions of plasma particles measured by spacecraft in the solar wind and many other space plasmas show enhanced suprathermal tails. The presence of suprathermal populations is characteristic of collisionless space plasmas not in thermal equilibrium. Such distributions can be fitted by different velocity distribution functions such as Kappa distributions decreasing as a power law of the velocity or with a sum of Maxwellian and Kappa with different temperatures. Including isotropic and anisotropic Kappa distribution functions greatly facilitates the description of plasma effects at small‐scales. Using solar wind observations from different spacecraft at different radial distances, we show the links between different plasma parameters like the number density, bulk velocity, temperature and anisotropy, and especially the kappa index associated to the halo population of suprathermal electrons. We also introduce the regularized Kappa distribution that prevents any diverging moment and allows a realistic model of the collisionless solar wind plasma. Pogorelov, Nikolai Solar Wind Interaction with the Local Interstellar Medium: Do Models Reproduce Observational Data? Federico Fraternale, University of Alabama in Huntsville, USA Michael Gedalin, Ben‐Gurion University, Israel Jacob Heerikhuisen, University of Waikato, New Zealand Tae Kim, University of Alabama in Huntsville, USA Grzegorz Kowal, University of Sao Paulo, Brazil Vadim Roytershteyn, Space Science Institute, Bolder, CO, USA Ming Zhang, Florida Institute of Technology, USA We present our recent results related to modeling of the interaction of the solar wind (SW) with the local interstellar medium (LISM). The main focus is made on the agreement of simulation results with the observational data from IBEX, New Horizons, and Voyagers. In addition, we discuss the large‐scale shape of the heliosphere and LISM parameters around it which agree with the observed anisotropy of TeV galactic cosmic rays. The effect of the SW and LISM turbulence is discussed on the instability of the heliopause caused by charge exchange and shear flows. Crossing of the heliospheric termination shock by non‐thermal ions is analyzed. 19TH ANNUAL INTERNATIONAL ASTROPHYSICS CONFERENCE ORAL ABSTRACTS

Pratt, Jane Diffusion and Dispersion in Anisotropic Magnetohydrodynamic Turbulence J. Pratt, Georgia State University, USA A. Busse, University of Glasgow, UK W.‐C. Mueller, TU Berlin, Germany Magnetohydrodynamic (MHD) turbulence structured by a large‐scale magnetic field is an essential aspect of interstellar or interplanetary plasmas. Here we investigate diffusion and dispersion in anisotropic MHD turbulence. We adopt the Lagrangian viewpoint, the natural point of view to study diffusion, and construct statistics based on the trajectories of Lagrangian tracer particles. From the motions of these tracer particles, we produce Lagrangian statistics such as single‐particle diffusion, two‐particle dispersion, and velocity autocorrelations. We also demonstrate new Lagrangian statistics developed to understand anisotropic turbulent dispersion. Simulation results will be presented that are performed using grid sizes up to 2048^3. Diffusion and transport processes in turbulent plasmas constitute fundamental astrophysical problems; a clear understanding of these processes is needed in order to produce improved theoretical models for the diffusion and transport of energetic particles, including cosmic rays. Rankin, Jamie Electrons and the Galactic Cosmic Ray Anisotropies in the Very Local Interstellar Medium Jamie Rankin, Princeton University, USA Amongst its many findings from beyond the heliopause, Voyager 1 discovered an unusual, unpredicted time‐varying anisotropy in galactic cosmic ray protons, characterized by a small (~15%), but lasting (~100 to ~630 days) depletion of particles traveling nearly perpendicular to the magnetic field, within an otherwise isotropic pitch angle distribution. Outside of this isolated region, cosmic rays appear largely uniform and isotropic, with no signs of a radial gradient and only occasional perturbations to their intensity. So far, the properties of these not‐yet‐fully‐understood events in the very local interstellar medium have been mainly studied using integrated proton intensities of ~20 MeV and higher. Here, we extend the analysis to electrons and lower‐energy protons, and report the unanticipated finding that, unlike their proton counterparts, ~3 to ~105 MeV electrons do not show clear evidence of the pitch angle anisotropy. We present galactic cosmic ray proton and electron observations using anisotropy data obtained by Voyager 1’s Cosmic Ray Subsystem, compare each species’ physical attributes, and discuss the implications of these unexpected observations. Raymond, John Anomalous Dropouts in Fully Stripped Ions John Raymond, CfA, Harvard University, USA Recent papers by Zhao et al. and Kocher et al. report ACE observations of intervals in the slow solar wind and in ICMEs when the abundances of fully stripped ions (He2+, C6+, N7+, and O8+) drop sharply compared to all other ions measured by ACE. Those papers list several possible causes, the most likely of which is related to resonant cyclotron heating, since they share the same M/Q and therefore cyclotron frequency. This talk attempts to determine where the anomalies are formed. It seems plausible that relatively dense blobs of gas at heights above about 3 ‐4 Rsun, above the ionization freeze‐in and collisional‐collisionless transition, but low enough that gravity still plays a role, suffer a reduction in turbulent heating. If there is insufficient power at the resonant frequency, those ions may fail to accelerate with the rest of the plasma. 19TH ANNUAL INTERNATIONAL ASTROPHYSICS CONFERENCE ORAL ABSTRACTS

Reisenfeld, Daniel Sounding the Dimensions of the Heliosphere with IBEX Daniel B. Reisenfeld, Los Alamos National Laboratory, USA Maciej Bzowski, Polish Academy of Sciences, Poland Herbert O. Funsten, Los Alamos National Laboratory, USA Jacob Heerikhuisen, University of Waikato, New Zealand Paul H. Janzen, University of Montana, USA Marzena A. Kubiak, Polish Academy of Sciences, Poland David J. McComas, Princeton University, USA Nathan A. Schwadron, University of New Hampshire, USA Justyna Sokol, Polish Academy of Sciences, Poland Eric J. Zirnstein, Princeton University, USA The IBEX mission has shown that variations in the ENA flux from the outer heliosphere are associated with the solar cycle. In particular, there is a good correlation between the dynamic pressure of the outbound solar wind and variations in the observed IBEX ENA flux. (McComas et al. 2017, 2019; Reisenfeld et al. 2016) There is, however, a time difference between observations of the outbound SW and the heliospheric ENAs with which they correlate, ranging from approximately two to four years, depending on ENA energy and look direction. This time difference can be used as a means of “sounding” the heliosheath, that is, finding the average distance to the ENA source region in a particular direction. We use IBEX ENA data from 2009 through mid‐2018, corrected for survival probability to the inner heliosphere (Bzowski, 2008), and limit ourselves to data from the nose‐ward hemisphere, divided into 33 “macro‐pixels”. As each point in the sky is sampled once every six months, this gives us a time series of 19 points per macro‐pixel on which to time correlate. For each map, a Ribbon removal method is applied so that the correlation is carried out with only the globally distributed flux. In calculating the response time, we account for the varying speed of the outbound solar wind by using a time and latitude dependent set of solar wind speeds derived from interplanetary scintillation observation data. (Sokol et al. 2015; Tokumaru et al. 2010) Consistent with heliospheric models, we find that the shortest distance to the heliopause is slightly south of the nose direction (d ~120 – 130 AU, with a flaring toward the flanks and poles (d ~160 – 180 AU). Richardson, John Voyager 2 Plasma data in the LISM John Richardson, MIT, USA John Belcher, MIT, USA Voyager 2 entered the LISM in late 2018. Although plasma data were good up to the heliopause crossing, in the LISM plasma currents are on the edge of what the plasma instrument can detect. We will show the time profile of currents in the LISM and where possible correlate with other instrument data. We will also show data from spacecraft rolls, when the side detector samples currents from 360 degrees of look directions and clearly samples LISM plasma and discuss how these data constrain the LISM plasma parameters. 19TH ANNUAL INTERNATIONAL ASTROPHYSICS CONFERENCE ORAL ABSTRACTS

Roelof, Edmond A Generalized Non‐Linear Compton‐Getting Transformation for Energetic Particles: Applications Throughout the Heliosphere Edmond C. Roelof, Johns Hopkins U./APL, USA The Compton‐Getting transformation (CGT), introduced in 1935 to describe anisotropies in galactic cosmic rays, has been used for most of the Space Age to interpret anisotropic intensities observed in energetic ion and neutral atoms. It follows from the invariance of the particles’ phase‐space density under the Lorentz velocity transformation between frames. It has been applied in two quite different manners. When the transform velocity is measured, the intensities in the spacecraft frame are transformed to those in the Lorentz frame, where they are interpreted based on some a priori assumptions of the physical processes operating therein, e.g., “diffusion‐ convection” or other forms of particle transport more easily described in the Lorentz frame. This approach has recently come under some stress with the Parker Solar Probe/ISOIS observations of low‐energy ion events near perihelion, because of their very steep differential spectra (slope ‐4.5) and extreme anisotropies (~20:1) that are inconsistent with strong local pitch‐angle scattering. In a very different regime, the CGT has proven essential in the interpretation of the intensities of energetic neutral atoms (ENAs) observed by IBEX and Cassini/INCA. On the other hand, energetic ion anisotropies have been used to infer the transform velocity itself, e.g., the bulk plasma velocity, under some a priori assumptions on the form of the anisotropies that should exist in the Lorentz frame. This latter approach has been used to supplement onboard plasma instruments themselves in deducing global plasma velocities in planetary magnetospheres (Earth, Jupiter, and Saturn) as well as in the solar wind and within the heliosheath that forms its transition to the interstellar medium. The diversity of these challenging tasks has led me to develop a generalized non‐linear mathematical theory of the CGT that can accommodate the whole range within a single analytic formulation. A brief overview of the new theory (whose formulas turn out to be remarkably simple to interpret physically) will be illustrated by applications to energetic particle observations from missions throughout the heliosphere: Parker Solar Probe, near‐Earth missions, Galileo/EPD, Cassini/INCA, New Horizons/PEPSSI, and Voyagers/LECP 1and 2. Savage, Sabrina Comparing Reconnection Outflow Observations in the Extended Solar Corona and Earth's Magnetotail Sabrina L. Savage, NASA/MSFC, USA Magnetic reconnection is a universal process for rapid energy release across a plethora of astrophysical contexts. Observational signatures of reconnection have been studied extensively in the lower solar corona for decades, successfully providing insight into energy release mechanisms in the region above post‐flare arcade loops and below 1.5 solar radii. During large eruptive events, however, energy release continues to occur well beyond the presence of reconnection signatures at these low heights. Supra‐arcade downflows (SADs) and downflowing loops (SADLs) are particularly useful measures of continual reconnection in the corona as they may indicate the presence and path of retracting post‐reconnection loops. The association of these features with magnetic reconnection increases the significance of understanding their genesis. SADs have been interpreted as density depressions behind newly reconnected and outflowing loops (SADLs). Models have shown the plausibility of this interpretation. We will present an on‐going study of complementary observations of magnetic reconnection detected via in situ instruments in the magnetosphere. These observations, provided by five THEMIS spacecraft, reveal similar structures and conditions to those related to SADs. We compare data from multiple SADs and dipolarization fronts to test the similarity between these plasma regimes, strongly favoring the interpretation of SADs as instabilities trailing retracting loops. Schwadron, Understanding the LISM with the IBEX Ribbon Nathan N. A. Schwadron, UNH, Princeton, USA D. J. McComas, Princeton, USA The Interstellar Boundary Explorer (IBEX) mission discovered the presence of a global structure in energetic neutral atom emissions from the outer heliosphere not predicted by any model ‐‐ the IBEX “ribbon”. In the search for possible explanations, observations have pointed to a likely source from neutral atoms produced through charge‐exchange with the outflowing solar wind, the secondary solar wind, which then undergoes charge‐exchange again beyond the heliopause within the very local interstellar medium. One mechanism invoked to explain the IBEX Ribbon involves the scattering of ions from counterstreaming Alfven waves on magnetic field lines within the Local Interstellar Medium (LISM) beyond the heliopause. A prediction from this mechanism is that the width of the Interstellar Ribbon at ~1 keV should be controlled almost exclusively by the Alfven speed within the compressed interstellar plasma beyond the heliopause. We utilize this concept to understand the conditions within the LISM plasma near our heliosphere, and narrow down the region in which the Ribbon forms. 19TH ANNUAL INTERNATIONAL ASTROPHYSICS CONFERENCE ORAL ABSTRACTS

Shalchi, Andreas Heuristic Description of Perpendicular Transport Andreas Shalchi, University of Manitoba, Canada The problem of the transport of energetic particles across a mean magnetic field is known since more than 50 years. Previous attempts to describe perpendicular transport theoretically were either based on complicated non‐linear theories or computationally expensive simulations. In either case it remained unclear how particles really experience perpendicular transport. In this talk I will present a new heuristic approach to solve this problem. Simple arguments will lead to several formulas for the perpendicular diffusion coefficient. These formulas include well‐known cases such as compound sub‐diffusion and the field line random walk limit but also newer cases such as the collisionless Rechester and Rosenbluth limit. Furthermore, analytical theories such as NLGC and UNLT theories contains a correction factor a^2 which is often assumed to be 1/3. The new heuristic approach explains this value as well. Shrestha, Bishwas Energetic Neutral Atom Flux from the Inner Heliosheath and its Connection to Termination Shock Properties L. Bishwas L. Shrestha, The University of Alabama in Huntsville, USA Eric J. Zirnstein, Princeton University, USA Jacob Heerikhuisen, The University of Waikato, NZ We present statistical comparisons between energetic neutral atom (ENA) fluxes obtained using a global simulation of the heliosphere and data collected by the Interstellar Boundary Explorer (IBEX) spacecraft. The simulation of the inner heliosheath (IHS) ENA flux is based on a 3D steady‐state heliosphere with a multi‐Maxwellian description of protons in the IHS. We perform a comparison to the Compton‐Getting and survival probability corrected data from the IBEX‐Hi instrument over the time period 2009‐2015. The statistical comparison is performed by calculating the chi‐square value between the simulated ENA fluxes and data for each line of sight in the sky. A comparison with exposure averaged data for solar minimum and solar maximum conditions is also performed to see the affect of SW properties on the IHS ENA fluxes. Our results show that the model matches well with the data in the flanks and some parts of the nose of the heliosphere, whereas, the match is poor in the downwind tail, ribbon, and polar regions. We interpret these results to mean that: (i) the heliosheath plasma in the polar region consists of advected fast (or slow) SW during solar minimum (or maximum) conditions, and (ii) the HTS parameters are likely different over poles due to coronal holes. A poor match at around 30 degree north and south of the downwind tail direction is likely due to the existence of a mixture of plasma in the heliosheath that comes from both fast and slow SW. Singh, Talwinder Coronal Mass Ejection Simulations in the Inner Heliosphere using a Data Constrained Modified Spheromak Model Talwinder Singh, UAH, USA Tae Kim, UAH, USA Nikolai Pogorelov, UAH, USA Charles N. Arge, NASA Goddard, USA The magnetic fields of interplanetary coronal mass ejections (ICMEs), which originate close to the Sun in the form of a flux rope, determine their geoeffectiveness. Therefore, robust flux rope‐based models of CMEs are required to perform magnetohydrodynamic (MHD) simulations aimed at space weather predictions. We will present a modified spheromak model and demonstrate its applicability to CME simulations. We will show how magnetic properties of a CME such as its poloidal and toroidal fluxes can be determined from observations. We will show a robust technique for introducing CMEs with an appropriate speed into a background, MHD solution describing the solar wind in the inner heliosphere. Through a parametric study, we find that the speed of a CME is much more dependent on its poloidal flux than on the toroidal flux. We also find that the initial size of the flux rope, as well as its plasma beta can be used to constrain the eruption speed of our model. We demonstrate the applicability of this model to CME‐ CME collision simulations. Finally, we use this model to simulate the 12 July 2012 CME and compare the plasma properties at 1 AU with observations. The predicted CME properties agree reasonably with observational data. Slavin, Jonathan Interstellar Dust and Gas in the Heliosphere Jonathan Slavin, Center for Astrophysics | Harvard & Smithsonian, USA Direct sampling of the interstellar medium (ISM) is only possible within the heliosphere. Though much of the interstellar dust and gas that is incident on the heliosphere is filtered either at the heliopause or further inside the heliosphere, the fraction that we are able to detect provides important clues to the nature of the surrounding Local Interstellar Cloud and the Local Bubble beyond that. Recent detections of supernova created dust on Earth have important implications for the history of the local ISM (LISM). We will discuss the state and history of the LISM as revealed by the in situ detections and other observations as well as recent numerical simulations that we have carried out. 19TH ANNUAL INTERNATIONAL ASTROPHYSICS CONFERENCE ORAL ABSTRACTS

Spence, Harlan HelioSwarm: Unlocking the Multiscale Mysteries of Weakly‐Collisional Magnetized Plasma Turbulence and Ion Heating Harlan Spence, University of New Hampshire, USA Kristopher Klein, University of Arizona, USA and the International HelioSwarm Mission Team In this presentation, we discuss the HelioSwarm mission and its implementation strategy. HelioSwarm is a NASA MidEx mission concept designed to reveal the three‐ dimensional, dynamic mechanisms controlling the physics of turbulence, a ubiquitous process occurring throughout the heliosphere and the universe at large. HelioSwarm resolves the transfer and dissipation of turbulent energy in weakly‐collisional magnetized plasmas with a novel configuration of spacecraft in the solar wind. These simultaneous multi‐point, multi‐scale measurements of space plasmas allow us to reach closure on two science goals comprised of six science objectives: (1) reveal how turbulent energy is transferred in the most probable, undisturbed solar wind plasma and distributed as a function of scale and time; (2) reveal how this turbulent cascade of energy varies with the background magnetic field and plasma parameters in more extreme solar wind environments; (3) quantify the transfer of turbulent energy between fields, flows, and ion heat; (4) identify thermodynamic impacts of intermittent structures on ion distributions; (5) determine how solar wind turbulence affects and is affected by large‐scale solar wind structures; and (6) determine how strongly driven turbulence differs from that in the undisturbed solar wind. HelioSwarm transforms our understanding of plasma turbulence using a first‐ever “swarm” of 9 spacecraft, comprised of a “hub” spacecraft and 8 “node” spacecraft. The swarm spacecraft co‐orbit in a P/2 lunar resonant Earth orbit, with a ~2 week period, an apogee of ~61Re and perigee of ~12Re. Swarm design and on‐board propulsion produce inter‐spacecraft separations both along and across the Sun‐Earth line in the regions of interest. As they co‐orbit, the swarm’s 36 baseline separations slowly evolve, enabling the swarm configurations to simultaneously sample the turbulent cascade at multiple points with inter‐spacecraft separations ranging from fluid scales (1000’s of km) to sub‐ion kinetic scales (10’s of km). Each node possesses an identical instrument suite that consists of a Faraday cup, a fluxgate magnetometer, and a search coil magnetometer. The hub has the same instrument suite as the nodes, plus an ion electrostatic analyzer. Other HelioSwarm mission details will also be described. Starkey, Michael MMS Observations of Accelerated He+ Pick‐up Ions at Quasi‐perpendicular Shocks M. J. Starkey, University of Texas San Antonio, Southwest Research Institute, USA S. A. Fuselier, Southwest Research Institute, University of Texa San Antonio, USA M. I. Desai, Southwest Research Institute, University of Texa San Antonio, USA R. G. Gomez, Southwest Research Institute, USA J. Mukherjee, Southwest Research Institute, USA I. J. Cohen, The John Hopkins Applied Physics Laboratory, USA S. J. Schwartz, Lboratory for Atmospheric and Space Physics, USA C. T. Russell, University of California Los Angeles, USA H. Lai, University of California Los Angeles, USA Interstellar pick‐up ions (PUI) are interstellar neutrals which have been ionized in transit through the Heliosphere via charge exchange or photoionization. These new PUI’s then ‘freeze’ into the solar wind (SW) and move with the bulk SW velocity (VSW). They also gyrate around the local magnetic field with VSW, resulting in a maximum PUI velocity of 2VSW. Helium in the SW is typically doubly charged and He+ is in very low abundance compared to bulk SW protons. Thus, He+ observed in the SW is typically of interstellar origin. The concentration of He+ is low enough to be treated as a test particle in the SW and this ion is used to track the evolution of PUI distributions as they encounter shocks in the SW. Understanding how He+ PUIs are accelerated at shocks in space provides valuable insights into shock dynamics and shock acceleration mechanisms, particularly for the termination shock, which is heavily influenced by SW PUIs. In this work we compare MMS observations of quasi‐perpendicular super‐critical shocks with varying θ_Bn and Mach number, in which accelerated He+ ions were observed downstream of the shock. In order to observe the PUI motion relative to the local magnetic field, we derive average 2‐D pitch angle distributions in the field aligned bulk plasma frame, as well as reduced 1‐D velocity distributions for selected upstream and downstream intervals. Our results indicate that PUIs are accelerated largely perpendicular to the local magnetic field. Furthermore, by comparing theoretical reflection ratios to measured ratios of accelerated ions, we find that shock reflection plays a major role in the acceleration of He+ PUIs, which increases with increasing Mach number and θ_Bn. 19TH ANNUAL INTERNATIONAL ASTROPHYSICS CONFERENCE ORAL ABSTRACTS

Sterling, Alphonse Recent and Forthcoming Studies of Solar Coronal Jets Alphonse C. Sterling, NASA/MSFC, USA Ronald L. Moore, University of Alabama in Huntsville, USA Navdeep K. Panesar, BAERI/LMSAL, USA Solar jets occur throughout the solar atmosphere, likely at a rate of hundreds per day. Observations at X‐ray and EUV wavelengths show that frequently jets are made by eruptions of small‐scale filaments, called “minifilaments.” Recent studies indicate that many, or even the majority of, these jet‐producing minifilament eruptions occur at locations where opposite‐polarity photospheric magnetic fluxes merge and cancel. These observations support the idea that flux cancelation builds a magnetic flux rope along which cool minifilament material gathers, and that the flux rope subsequently erupts to form the jet through a sequence of magnetic reconnections. If the erupting minifilament field contains twist, it could transfer that twist only the ambient coronal field via reconnection. Moreover, if the ambient field opens into the heliosphere, it is plausible that the twist propagates out into the solar wind, possibly appearing as a “switchback” magnetic structure recently discovered by Parker Solar Probe. In this presentation we will update our recent investigations into jets, and discuss expectations for jet studies with new Sun‐observing instruments. Strauss, Du Toit Perpendicular Diffusion of Solar Energetic Particles: Recent Progress and Outstanding Issues Du Toit Strauss, North‐West University, South Africa Jabus van den Berg, North‐West University, South Africa Ruhann Steyn, North‐West University, South Africa Multi‐spacecraft observations of widespread solar energetic particle (SEP) events indicate that perpendicular (to the mean field) diffusion is an important SEP transport mechanism. However, this is in direct contrast to so‐called spike and drop‐out events, which indicate very little lateral transport. To better understand these seemingly incongruous observations, we discuss the recent progress made towards understanding and implementing perpendicular diffusion in transport models of SEP electrons. This includes a re‐derivation of the relevant focused transport equation, a discussion surrounding the correct form of the pitch‐angle dependent perpendicular diffusion coefficient and what turbulence quantities are needed as input, and how models lead to degenerate solutions of the particle intensity. Lastly, we evaluate the validity of a diffusion approach to SEP transport and conclude that it is valid when examining a large number of (an ensemble of) events, but that individual SEP events may exhibit a coherent structure related to the magnetic field turbulence at short timescales that cannot be accounted for in this modelling approach. Strumik, Marek Global 2D MHD Simulations of the Heliospheric Current Sheet in the Inner Heliosheath Marek Strumik, Polish Academy of Sciences, Poland The heliospheric current sheet (HCS) separates regions of different magnetic polarity in the heliosphere. It is transported by approximately radial plasma flow from the inner heliosphere toward the inner heliosheath, where the flow slows down, diverges and becomes nonradial. This influences the transport of HCS, which results in a complicated structure of HCS foldings and a massive pile‐up of sectors of the opposite magnetic polarity. Additionally, due to gradual slowdown of the plasma flow, magnetic‐reconnection instabilities have more time for development and the reconnection can be expected to intensify. Small thickness of HCS makes it difficult to incorporate it into 3D global numerical models of the heliosphere. Also plasmoid instability of extended current sheets requires very‐high‐resolution numerical models, which is related to a huge computational effort in the case of 3D models. I present results of global 2D MHD numerical simulations with HCS included, that can provide some insight into HCS‐related processes in the inner heliosheath. I focus on the problem of annihilation of magnetic sectors in the proximity of the heliopause, that provides a solution to the magnetic‐ sector pile‐up problem in the inner heliosheath. Possible consequences for the global heliospheric structure will be discussed as well. 19TH ANNUAL INTERNATIONAL ASTROPHYSICS CONFERENCE ORAL ABSTRACTS

Tang, Bofeng Numerical Modeling of Suprathermal Electron Transport in the Solar Wind: Effects of Whistler Turbulence Bofeng Tang, The University of Alabama in Huntsville Gary P. Zank, The University of Alabama in Huntsville Vladimir I. Kolobov, The University of Alabama in Huntsville The solar wind electron velocity distribution function (VDF) deviates significantly from an equilibrium Maxwellian distribution, and is comprised of a Maxwellian core, a suprathermal halo, a field‐ aligned component strahl, and a higher energy superhalo. Wave‐particle interactions associated with whistler wave turbulence are introduced into the kinetic transport equation to describe the interaction between the suprathermal electrons and the whistler waves. A numerical method has been developed to solve the Fokker‐Planck kinetic transport equation with only diagonal diffusion tensor. Application of the numerical method to suprathermal electrons in the solar wind in the presence of whistler waves is presented. Comparison and analysis between the numerical results and observations are made. An extended numerical method for the Fokker‐Planck kinetic transport equation with a full diffusion tensor is introduced. Preliminary results of the full diffusion tensor solver are presented. Comparisons with the previous diagonal diffusion tensor solver are made. Tasnim, Samira Outer Heliospheric Turbulence and the Angular Broadening of Radio Sources from the Voyager Data Samira Tasnim, UAH, USA Gary P. Zank, UAH, USA Iver H. Cairns, University of Sydney, AUSTRALIA Laxman Adhikari, UAH, USA The amplitude of fluctuating density turbulence is important in estimating the angular broadening of radio sources in the outer heliosphere or very local interstellar medium (VLSIM). We calculate the density variance, inner scale, correlation length of the velocity, the Alfven velocity, and wave number as a function of radial distance using plasma and magnetometer data from the Voyager 2 spacecraft over the period 1977 to 2018. We use a power spectral analysis to determine the observed density turbulence amplitude which includes an inner scale over the energy containing range and the inertial range as a function of wave number. We compare the Voyager data determined turbulence amplitude with the density turbulence model of Zank et al., 2017 and the results of Bellamy and Cairns, 2005. The various results show strong similarities, both qualitatively and quantitatively. The predicted turbulence amplitudes also show similar radial trends as those observed. We also analytically solve for the scattering angle as a function of radial distance. Comparison with Voyager data indicates that the radiation source is located in VLISM. The further analysis will directly extract the scattering angle using numerical methods and compare them with the analytic results. TenBarge, Jason A Field‐Particle Correlation Analysis of a Continuum Vlasov‐Maxwell Perpendicular Collisionless Shock Jason TenBarge, PU, USA James Juno, UMD, USA Gregory Howes, UI, USA Collisionless shocks play an important role in space and astrophysical plasmas by irreversibly converting the energy of the incoming supersonic plasma flows into other forms, including plasma heat, particle acceleration, and electromagnetic field energy. Here we present the application of the field‐particle correlation technique to a simulation of an idealized perpendicular magnetized collisionless shock to understand the transfer of energy from the incoming flow into these other forms through the structure of the shock. We employ the fully kinetic Eulerian Vlasov‐Maxwell component of the Gkeyll simulation framework to perform the perpendicular shock simulation and identify the velocity‐ space signature of shock‐drift acceleration of the ions in the shock foot, as well as the velocity‐space signature of adiabatic electron heating through the shock ramp. 19TH ANNUAL INTERNATIONAL ASTROPHYSICS CONFERENCE ORAL ABSTRACTS van Marle, Allard On the Contribution of low‐mach, high‐beta Shocks to the Cosmic Ray Spectrum Jan Allard Jan van Marle, UNIST, South Korea Astrophysical shocks accelerate particles through the Fermi acceleration process, which involves a charged particle repeatedly crossing the shock after being reflected by the local magnetic field and gaining momentum. Eventually, the particles reach relativistic speeds and can be observed as cosmic rays. This is a self self‐sustaining interaction because the presence of non‐thermal particles in the shock‐region causes instabilities in the magnetic field, which in turn allow the magnetic field to reflect the particles. This process has been studied extensively in the case of high‐Mach, low‐beta shocks, such as those that are found in stellar wind collisions and supernovae. However, there are astrophysical shocks, such as those that occur in colliding galaxy clusters, that are characterized by a low sonic Mach number, combined with a high plasma‐beta. So far, these shocks have been largely neglected and little is known about their ability to accelerate particles. Using a combined PIC‐MHD code, we have performed a series of numerical simulations of low‐Mach, high‐beta shocks, to investigate the interaction between the particles and the magnetic field under such conditions. We find that even low‐Mach shocks are capable of accelerating charged particles. However, due to the behaviour of the magnetic field, the process tends to be relatively inefficient, reducing the effective contribution to the cosmic ray spectrum. Furthermore, the interaction tends to radically change the nature of the shock itself, which indicates that further study is required to quantify the shocks' long‐term behaviour. Viall, Nicholeen Nine Outstanding Questions in Solar Wind Physics Joe Borovsky, Space Science Institute As a part of the American Geophysical Union’s Centennial celebration, the Journal of Geophysical Research commissioned papers on the Grand Challenges in the Earth and Space Sciences. We present our Grand Challenge paper on nine outstanding questions of solar wind physics that synthesizes input from the community. These questions are part of three overarching themes: 1) the formation of the solar wind, 2) interpreting observations of solar wind parcels, and 3) physical mechanisms operating on solar wind formation and evolution. We describe the current state of research in the field of solar wind physics, an updated framework for discussing solar wind formation, and future needs and opportunities for progress, with a focus on those that are unique to the measurements made by Parker Solar Probe and Solar Orbiter. Washimi, Haruichi Computational Analysis of Three‐Dimensional and Time‐Varying Outer Heliospheric Structure Using OMNI Solar Wind Plasma Daily Data at 1 AU from The Sun Haruichi Washimi, Kyushu University, Japan Takashi Tanaka, Kyushu University, Japan Gary P. Zank, University of Alabama in Hunstville, USA Shuichi Matsukiyo, Kyushu University, Japan We present a new MHD simulation method that uses OMNI solar wind plasma data to study the long‐time variability of the outer heliospheric structure. To perform highly efficient computations, two connecting spherical simulation boxes, one extending from 1AU to 20AU (1st box) from the Sun and the other from 20AU to 900AU (2nd box), are utilized. The daily OMNI plasma data are assigned on the inner boundary surface at 1AU of the 1st Box by assuming a corotating solar wind in longitudinal coordinates and that the solar‐wind ram‐pressure is independent of latitude. The simulation results at the outer boundary of the 1st Box at 20 AU are treated as the inner boundary conditions, i.e., at 20 AU, of the 2nd Box. Based on simultaneous simulations in both boxes, we simulate the response of the outer heliosphere to the variable solar wind as observed at 1 AU. Although individual and local phenomena are not necessarily well reproduced, we expect that some global and temporal heliospheric phenomena will be reproduced well by this method. Our temporal simulation starts at the beginning of 2000 and ends at the beginning of 2019, meaning that the simulation covers the time when Voyager 1 and 2 were in interplanetary space until the time when both Voyager 1 and 2 passed the heliopause. Preliminary results will be presented. 19TH ANNUAL INTERNATIONAL ASTROPHYSICS CONFERENCE ORAL ABSTRACTS

Westlake, Joseph Heliospheric Maps from Cassini INCA Early in the Cruise to Saturn D. G. Mitchell, JHU/APL, USA M. Gkioulidou, JHU/APL, USA K. Dialynas, Office of Space Research and Technology, Greece I. J. Cohen, JHU/APL, USA S. Krimigis, JHU/APL, USA R. B. Decker, JHU/APL, USA D. L. Turner, JHU/APL, USA A. K. Higginson, JHU/APL, USA G. Clark, JHU/APL, USA We present new energetic neutral atom (ENA) maps from the Ion and Neutral Camera (INCA) instrument on Cassini from the year 2000, prior to Cassini’s encounter with Jupiter. These ENA images span the energy range from 5‐55 keV covering the pickup to suprathermal energy range. Cassini attained these images at the peak of solar cycle 23 in interplanetary space with Jovian upstream ions representing the most significant source of potential backgrounds. As such, these images represent a novel glimpse into the influence of the solar cycle on the structure of the outer heliosphere, specifically on the heliosheath where pickup and suprathermal ions dominate. The observations are consistent with the picture of the heliosheath from previous observations by the Cassini, IBEX, and Voyager missions with slight latitudinal and longitudinal asymmetries. Wood, Brian New Observational Constraints on Stellar Winds and Astrospheres from the Hubble Space Telescope Brian E. Wood, Naval Research Laboratory, USA Hans‐Reinhard Mueller, Dartmouth College, USA New observational constraints on stellar winds and astrospheres have recently become available from the Hubble Space Telescope, particularly with regards to the winds of M dwarf stars. Interest in M dwarf winds is currently very high due to the discovery of a number of Earth‐like planets in the habitable zones around M dwarf stars, leading to substantial interest in the stellar environments for these planets and their atmospheres. Coronal winds emanating from solar‐like stars can only be detected via the hydrogen Lyman‐alpha absorption created in the wind/ISM interaction region. A spectroscopic survey of the Lyman‐alpha lines of 9 nearby M dwarfs has recently been completed, with 6 f the targets yielding successful detection of the astrospheric absorption signature. Analysis is still underway, but the study clearly shows that most M dwarfs have winds significantly weaker than that of the Sun. Wu, Chin‐Chun Global Magnetohydrodynamic Simulation Model for Studying Long‐term Variations of the Background Solar Wind Chin‐Chun Wu, Naval Research Laboratory, USA Kan Liou, The Johns Hopkins University, USA In this study, a global MHD simulation model is used to test the long‐term performance of a newly developed scheme for the background solar wind condition at 18 Rs (Wu et al., Solar Physics, 2020). The scheme is based on the Wang‐Sheeley model of the solar wind speed (V ~ fs‐α, where fs is the magnetic flux expansion factor and α is a free parameter) and is optimized by matching MHD simulation results with in situ solar wind measurements at 1 AU over a solar quiet Carrington rotation: V18Rs = (51.8 + 196.4 α) + (253.6 + 607.1α) fs‐α. The magnetic field strength is obtained from extrapolation of photospheric synoptic map to 2.5 Rs using the potential‐field source‐surface (PFSS) model and to 18 Rs using conservation of flux tube. To estimate the solar wind density and temperature at 18 Rs, we assume an incompressible solar wind and a constant total pressure. We perform global MHD simulations of the solar wind over a solar cycle (1996 to 2008) using the above scheme with eight different α values (0.2, 0.3, … 0.9). Results will be compared with in situ solar wind measurements from the Wind spacecraft. We will calculate a number of forecast accuracy metrics to determine the best α value and present the result. 19TH ANNUAL INTERNATIONAL ASTROPHYSICS CONFERENCE ORAL ABSTRACTS

Yalim, Mehmet Effects of Cowling Resistivity in the Weakly‐Ionized Chromosphere Sarp Mehmet Sarp Yalim, University of Alabama in Huntsville, USA Avijeet Prasad, University of Alabama in Huntsville, USA Nikolai V. Pogorelov, University of Alabama in Huntsville, USA Gary P. Zank, University of Alabama in Huntsville, USA The chromosphere is a very complex region to model physically and solve numerically. The plasma temperature increases from the photosphere to corona from O(10^3) K to O(10^6) K through the chromosphere and the transition region in only ~10,000 km. Certain regions of the solar atmosphere are at sufficiently low temperatures with a low ionization rate to be considered as weakly‐ionized. In particular, this is applicable to the lower chromosphere. This leads to Cowling resistivity values that are orders of magnitude greater than the Coulomb resistivity, and thus to anisotropic dissipation in Ohm’s law. In order to evaluate the expression for the Cowling resistivity (Cowling, 1976), the external magnetic field strength and an estimate for the neutral fraction as a function of the bulk plasma density and temperature are required. We obtain the magnetic field topology from the non‐force‐free field (NFFF) extrapolation technique (Hu & Dasgupta, 2008;Hu et al., 2010) based on SDO/HMI vector magnetogram data, and the stratified density and temperature profiles from the VAL‐C model (Vernazza et al., 1981) based on Skylab observations. Accordingly, we follow the formulations in Leake & Arber, 2006 to calculate the Cowling resistivity. We investigate the variation and effects of Cowling resistivity in the chromosphere in the course of evolution of active regions that result in eruptive flares. Particular focus is given to its possible effect on magnetic reconnection. References: ‐ Cowling, T. G. (1976), Magnetohydrodynamics, Monographs on Astronomical Subjects, Adam Hilger. ‐ Hu, Q. & Dasgupta, B. (2008), An improved approach to non‐force‐free coronal magnetic field extrapolation, Sol. Phys., 247, 87–101. ‐ Hu, Q., Dasgupta, B., DeRosa, M. L., Buchner, J., & Gary, G. A. (2010), Non‐force‐free extrapolation of solar coronal magnetic field using vector magnetograms, JASTP, 72, 219– 223. ‐ Leake, J. E., & Arber, T. D. (2006), The emergence of magnetic flux through a partially ionized solar atmosphere, A&A, 450, 805–818. ‐ Vernazza, J. E., Avrett, E. H., & Loeser, R. (1981), Structure of the solar chromosphere. III. Models of the EUV brightness components of the quiet Sun, ApJS, 45, 635–725. Zank, Gary Compressible and Incompressible Magnetic Turbulence Observed in the Very Local Interstellar Medium by Voyager 1 G.P. Zank, University of Alabama in Huntsville, USA M. Nakanotani, University of Alabama in Huntsville, USA G.M. Webb, University of Alabama in Huntsville, USA Voyager 1 observed Kolmogorov‐like compressible turbulence just upwind of the heliopause (Burlaga et al., 2015). Subsequent measurements by Voyager 1 further from the heliopause revealed that the observed fluctuations were now fully incompressible, with a Kolmogorov‐like spectrum that was essentially identical to that of the earlier compressible spectrum (Burlaga et al., 2018). Zank et al., 2017a showed that only compressible fast magnetosonic modes could be transmitted from the inner heliosheath into the very local interstellar medium (VLISM), and could exhibit a Kolmogorov spectrum. We show here that the small plasma beta VLISM admits three‐wave interactions between a fast magnetosonic mode, a zero‐frequency mode, and an Alfven wave. The fast magnetosonic mode is converted to an incompressible Alfven (or zero‐frequency) mode with wave number almost identical to that of the initial compressible fast mode. The initial compressible and generated incompressible spectra are essentially identical. For the wavelength range observed by Voyager 1, we estimate that compressible fast modes are fully mode converted to incompressible fluctuations within ~10 au of the heliopause. We suggest that the VLISM magnetic field spectrum is a superposition of a higher amplitude Kolmogorov spectrum of heliospheric origin with an estimated correlation length ~30 au, having a minimum wave number ~1/100)/(au), and a lower amplitude (possibly local) ISM Kolmogorov spectrum, the latter possessing an outer scale > 2 pc. We suggest that the transmission of compressible turbulence from an inner asterosheath into the local circumstellar interstellar medium surrounding a star, and the subsequent mode conversion to incompressible turbulence, may be a general mechanism by which stars drive turbulence in the interstellar medium. 19TH ANNUAL INTERNATIONAL ASTROPHYSICS CONFERENCE ORAL ABSTRACTS

Zhao, Lingling ACR Proton Acceleration Associated with Reconnection Processes Beyond the Heliospheric Termination Shock L.‐L. Zhao, University of Alabama in Huntsville, USA G. P. Zank, University of Alabama in Huntsville, USA Q. Hu, University of Alabama in Huntsville, USA Y. Chen, University of Alabama in Huntsville, USA L. Adhikari, University of Alabama in Huntsville, USA J. A. leRoux, University of Alabama in Huntsville, USA A. Cummings, California Institute of Technology, USA E. Stone, California Institute of Technology, USA L. F. Burlaga, NASA Goddard Space Flight Center, USA One of the curious observations from the Voyagers is that the intensity of anomalous cosmic rays ( ACRs) did not peak at the heliospheric termination shock ( HTS) but instead a short distance (within ∼1 au) downstream of the HTS. One possible explanation is that the interaction of the wavy heliospheric current sheet with the HTS enhances magnetic reconnection and generates numerous small‐scale magnetic flux ropes in the heliosheath immediately downstream of the HTS. Charged particles are accelerated in this region due to Fermi acceleration and the reconnection electric field. In this work, we provide observational evidence of the presence of magnetic flux ropes in the heliosheath region just downstream of the HTS using a wavelet analysis of the reduced magnetic helicity and Grad–Shafranov reconstruction techniques. The Zank et al. kinetic transport theory for particles propagating through the magnetic islands region is employed to fit the observed energetic proton intensities in the post‐HTS region. Our modeling results agree reasonably well with the observations, which suggests that stochastic acceleration via reconnection processes can explain the ACR proton peak beyond the HTS. Zharkova, Particle Acceleration in 3D Current Sheets with Magnetic Islands and their Diagnostics from In‐situ Observations Valentina Zharkova V., Northumbria University, United Kingdom Xia Q. , Northumbria University, United Kingdom Khabarova O., IZMIRAN, Russian Federation Malandraki O., National Observatory of Athens, Greece Using particle‐in‐cell (PIC) approach we investigate acceleration of particles during their passage through reconnecting current sheets occurring in the solar corona and interplanetary space. We investigate particle acceleration in 3D Harris‐type reconnecting current sheets with a single or multiple X‐nullpoints taking into account the ambient plasma feedback to the presence of accelerated particles The PIC approach is also used to evaluate the existing particle acceleration using transport equations.. For multiple X‐ nullpoints we consider coalescent and squashed magnetic islands formed in the current sheets with different thicknesses, ambient density and mass ratios for different magnetic field topologies, and simulate energy, density and pitch‐angle distributions of accelerated particles. We report distinct populations of two groups of particles, transit and bounced ones, which have very different energy and asymmetric pitch‐angle distributions associated with the magnetic field parameters. The simulated pitch angle distributions of accelerated particles are presented for a few cross‐sections of the spacecraft paths through the current sheets with and without magnetic islands and the outcomes are compared with some in‐situ observations of solar wind particles. We discuss locally re‐accelerated superthermal electrons and their relationship to the counter‐ streaming ‘strahls’ often observed in the pitch‐angle distribution spectrograms of the satellites crossing local current sheets. 19TH ANNUAL INTERNATIONAL ASTROPHYSICS CONFERENCE ORAL ABSTRACTS

Zirnstein, Eric Response of Pickup Ions in the Very Local Interstellar Medium to Solar Variations: Implications for the Evolution of the IBEX Ribbon and Interstellar Helium E. J. Zirnstein, Princeton University, USA T. K. Kim, University of Alabama in Huntsville, USA P. Mostafavi, Johns Hopkins University APL, USA J. Heerikhuisen, University of Waikato, NZ D. J. McComas, Princeton University, USA N. V. Pogorelov, University of Alabama in Huntsville, USA The Interstellar Boundary Explorer (IBEX) observes the “ribbon” of enhanced energetic neutral atom (ENA) fluxes from the outer heliosphere. The ribbon flux is likely formed from the neutralization of energetic pickup ions (PUIs) gyrating in the interstellar magnetic field outside the heliopause. Voyager 1 crossed the heliopause in 2012 and has observed several shocks in the very local interstellar medium (VLISM) which likely originate from merged interaction regions in the inner heliosphere that propagated outside the heliopause. We simulate the response of PUIs and the IBEX ribbon flux to solar disturbances propagating into the VLISM. First, we show that PUIs outside the heliopause respond significantly to the dynamic neutralized solar wind (SW) via charge‐exchange and to interactions with shocks via adiabatic heating/cooling. However, the evolution of ribbon fluxes at 1 au are primarily driven by changes in the neutralized SW and not PUI interactions with shocks outside the heliopause. Comparisons with IBEX observations of the ribbon at 1.1 keV show that an abrupt decrease in ENA fluxes observed in 2012 was caused by a drop in SW (and thus neutralized SW) speed by ~100 km/s. Our simulation predicts a recovery of 1.1 keV ribbon fluxes starting in 2019 to levels observed early in the mission due to an increase in SW speed. We also estimate that the presence of interstellar helium in the VLISM reduces the effectiveness of charge‐exchange sources for PUIs and reduces the model ribbon flux at 1 au by ~40%, matching well with IBEX ribbon fluxes. Zou, Ying Azimuthal Variation of Magnetic Reconnection at the Earth's Magnetopause Brian M. Walsh, Boston University, USA Emil Atz, Boston University, USA Haoming Liang, University of Alabama in Huntsville, USA Qianli Ma, Boston University, USA Vassilis Angelopoulos, UCLA, USA Magnetic reconnection extracts energy from the solar wind to power plasma convection, auroral displays, and geomagnetic substorms and storms in Earth’s magnetosphere. Although reconnection is often pictured as a two‐dimensional laminar process, where oppositely directed magnetic field lines in a plasma break and reconnect, the actual reconnection is three‐dimensional where it varies along the direction perpendicular to the plane. Since the scale in the 3rd dimension determines how much energy is imparted to the magnetosphere, knowledge of how reconnection varies in this direction, and what causes the variation is extremely important. Among existing reports, the utilized spacecraft constellations are often too small, or too large, only loosely constraining the range of 3rd‐dimension variability. Here we use serendipitous constellations with a spatial size that is right at the predicted scale for reconnection to vary. Our results show that reconnection jets transition from being present to absent within tenths of Earth radius. The sharp transition of reconnection is associated with spatially varying waves. Causes of the transition cannot be identified from the surrounding or upstream electromagnetic field and plasma conditions, implying that reconnection may naturally have a finite extent at certain stages of its development.