DOCSLIB.ORG

Space Weather Lecture 2: the Sun and the Solar Wind

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Space Weather Lecture 2: the Sun and the Solar Wind Space Weather Lecture 2: The Sun and the Solar Wind Elena Kronberg (Raum 442) [email protected] Elena Kronberg: Space Weather Lecture 2: The Sun and the Solar Wind 1 / 39 The radiation power is '1.5 kW·m−2 at the distance of the Earth The Sun: facts Age = 4.5×109 yr Mass = 1.99×1030 kg (330,000 Earth masses) Radius = 696,000 km (109 Earth radii) Mean distance from Earth (1AU) = 150×106 km (215 solar radii) Equatorial rotation period = '25 days Mass loss rate = 109 kg·s−1 It takes sunlight 8 min to reach the Earth Elena Kronberg: Space Weather Lecture 2: The Sun and the Solar Wind 2 / 39 The Sun: facts Age = 4.5×109 yr Mass = 1.99×1030 kg (330,000 Earth masses) Radius = 696,000 km (109 Earth radii) Mean distance from Earth (1AU) = 150×106 km (215 solar radii) Equatorial rotation period = '25 days Mass loss rate = 109 kg·s−1 It takes sunlight 8 min to reach the Earth The radiation power is '1.5 kW·m−2 at the distance of the Earth Elena Kronberg: Space Weather Lecture 2: The Sun and the Solar Wind 2 / 39 The Solar interior Core: 1H +1 H !2 H + e+ + n + 0.42 MeV 1H +2 He !3 H + g + 5.5 MeV 3He +3 He !4 He + 21H + 12.8 MeV The radiative zone: electromagnetic radiation transports energy outwards The convection zone: energy is transported by convection The photosphere – layer which emits visible light The chromosphere is the Sun’s atmosphere. The corona is the Sun’s outer atmosphere. Elena Kronberg: Space Weather Lecture 2: The Sun and the Solar Wind 3 / 39 The Solar interior Elena Kronberg: Space Weather Lecture 2: The Sun and the Solar Wind 4 / 39 Photosphere: sunspots Sunspots B=0.3·108 nT Elena Kronberg: Space Weather Lecture 2: The Sun and the Solar Wind 5 / 39 6 12 For most solar phenomena Rm ' 10 − 10 ) the magnetic field is “frozen” to the plasma. The Sun and its Magnetohydrodynamics The induction equation is ¶B = r × (v × B) + hr2B, (1) ¶t where v is the fluid velocity, B is the magnetic field strength, h = 1/(m0s) is the magnetic diffusivity, m0 is the permeability of free space and s0 is the electrical conductivity of the material. The magnetic Reynolds number is vL R = = m s vL. (2) m h 0 0 Elena Kronberg: Space Weather Lecture 2: The Sun and the Solar Wind 6 / 39 The Sun and its Magnetohydrodynamics The induction equation is ¶B = r × (v × B) + hr2B, (1) ¶t where v is the fluid velocity, B is the magnetic field strength, h = 1/(m0s) is the magnetic diffusivity, m0 is the permeability of free space and s0 is the electrical conductivity of the material. The magnetic Reynolds number is vL R = = m s vL. (2) m h 0 0 6 12 For most solar phenomena Rm ' 10 − 10 ) the magnetic field is “frozen” to the plasma. Elena Kronberg: Space Weather Lecture 2: The Sun and the Solar Wind 6 / 39 Frozen-in condition Credit: A. Brekke Elena Kronberg: Space Weather Lecture 2: The Sun and the Solar Wind 7 / 39 The Sun and its Magnetohydrodynamics The momentum equation is dv r = −rp + j × B + rg, (3) dt where r is the plasma density, p is the plasma pressure and g is the gravitational acceleration. Equating the left-hand side to the magnetic force in order of magnitude gives a speed of B v = p = vA, (4) m0r where vA is the Alfven´ speed and is the typical speed to which magnetic forces can accelerate plasma. Elena Kronberg: Space Weather Lecture 2: The Sun and the Solar Wind 8 / 39 The Sun and its Magnetohydrodynamics The continuity equation dr + rr · v = 0, (5) dt and energy equation rg d p j2 = −r · (krT) − r2Q(T) + (6) g − 1 dt rg s which describes how the entropy of a moving element of plasma changes because of three effects on the right-hand side: the conduction of heat, which tends to equalize temperatures along the magnetic field, k is the thermal conductivity the optically thin radiation, with a temperature dependence Q(T) ohmic heating. More details on MHD equations and their use in modeling of the Sun are e.g. in Priest, Magnetohydrodynamics of the Sun, 2014. Elena Kronberg: Space Weather Lecture 2: The Sun and the Solar Wind 9 / 39 Photosphere: sunspot generation mechanism Babcock-Leighton mechanism Credit: Sanches et al., 2014 Elena Kronberg: Space Weather Lecture 2: The Sun and the Solar Wind 10 / 39 Photosphere: sunspots Credit: S. Tiwari Elena Kronberg: Space Weather Lecture 2: The Sun and the Solar Wind 11 / 39 Photosphere: sunspots Credit: S. Tiwari Elena Kronberg: Space Weather Lecture 2: The Sun and the Solar Wind 11 / 39 Photosphere: sunspots Quiet sunspot, granulation Elena Kronberg: Space Weather Lecture 2: The Sun and the Solar Wind 12 / 39 Photosphere: sunspots Huge Hurrican Elena Kronberg: Space Weather Lecture 2: The Sun and the Solar Wind 13 / 39 Solar cycle Number of solar spots changes – solar cycle – 11 years Elena Kronberg: Space Weather Lecture 2: The Sun and the Solar Wind 14 / 39 Photosphere: solar flare Flare is a sudden flash of brightness observed near the Sun’s surface X-rays and UV radiation emitted by solar flares can affect Earth’s ionosphere and disrupt long-range radio communications. Direct radio emission at decimetric wavelengths may disturb the operation of radars and other devices that use those frequencies. It is impossible to predict solar flare. Elena Kronberg: Space Weather Lecture 2: The Sun and the Solar Wind 15 / 39 Chromosphere: Prominence Prominence is an arc of gas that erupts from the surface of the Sun The magnetic field is embedded in plasma – frozen-in condition Magnetic field strength is 106 –107 nT Elena Kronberg: Space Weather Lecture 2: The Sun and the Solar Wind 16 / 39 Prominence, Solar Flare and Coronal Mass Enjection Credit: SSL Berkely Elena Kronberg: Space Weather Lecture 2: The Sun and the Solar Wind 17 / 39 Solar Flare and CME Energy comparison: Large Solar flare '1020 Candy bars (250 Cal each) Earthquake (magnitude 8.0) '1010 Candy bars Credit: SSL Berkely Elena Kronberg: Space Weather Lecture 2: The Sun and the Solar Wind 18 / 39 Coronal Mass Ejections (CMEs) Elena Kronberg: Space Weather Lecture 2: The Sun and the Solar Wind 19 / 39 Solar Proton Event A solar proton event (SPE), or ”solar radiation storm”, occurs when particles (mostly protons) emitted by the Sun become accelerated either close to the Sun during a flare or in interplanetary space by CME shocks. Elena Kronberg: Space Weather Lecture 2: The Sun and the Solar Wind 20 / 39 Coronal Mass Ejection Elena Kronberg: Space Weather Lecture 2: The Sun and the Solar Wind 21 / 39 Coronal Holes Dark regions where the magnetic field is open and through which the solar wind is streaming outward. The strength of magnetic field at the poles is ∼105 nT Elena Kronberg: Space Weather Lecture 2: The Sun and the Solar Wind 22 / 39 Solar wind topology The Sun has a complex magnetic field geometry Coronal helmet streamers are large closed magnetic loops which connect regions of opposite magnetic polarity. They lead to formation of heliopsheric current sheets. Elena Kronberg: Space Weather Lecture 2: The Sun and the Solar Wind 23 / 39 Solar Corona The total eclipse of 29 March 2006 in Libya Credit: M. Druckmuller and P. Aniol Elena Kronberg: Space Weather Lecture 2: The Sun and the Solar Wind 24 / 39 Solar Corona Elena Kronberg: Space Weather Lecture 2: The Sun and the Solar Wind 25 / 39 The Solar wind Solar wind is a plasma, gas of charged particles with equal numbers of free positive and negative charge carriers Mainly electrons and protons, He (5%) Free charges make the plasma highly electrically conductive −3 5 Density ne,sw '5 cm and temperature Te,sw '10 K (room '293 K) Interplanetary Magnetic field (IMF) Bsw '5 nT at the Earth Velocity vsw ' 300 − 800 km/s Elena Kronberg: Space Weather Lecture 2: The Sun and the Solar Wind 26 / 39 Solar wind evidence Particles streaming from the Sun exert pressure upon interplanetary matter, evident from observations of comet tails. Churimov-Gerasimenko Comet obseved by Rosetta. Image Credit: ESA Elena Kronberg: Space Weather Lecture 2: The Sun and the Solar Wind 27 / 39 Solar Wind Flux Tube Conservation of the magnetic flux within the tube r 2 B(r) dA = B dA R 0 0 0 or R 2 B(r) = B 0 r The solar corona and any fixed source are rotating at an angular rate of 2p rad w = 25.4 days = 2.7 × 10−6rad s−1 Elena Kronberg: Space Weather Lecture 2: The Sun and the Solar Wind 28 / 39 Solar Wind Flux Tube The azimuthal plasma velocity in frame of reference rotating with the Sun Vf = −wr The magnetic field follows the plasma flow B V −wr f = f = Br Vr V(r) This gives a differential equation for the field lines near the solar equator rdf −wr = dr V(r) If V(r) is constant and location of the source is at f0, r = R then V r − R = − (f − f ). w 0 This geometry is known as the spiral of Archimedes. Elena Kronberg: Space Weather Lecture 2: The Sun and the Solar Wind 29 / 39 Interplanetary magnetic field (IMF) topology Due to the conservation of angular momentum of the plasma, the IMF lines trace out Archimedian spiral patterns (called Parker spiral).
Load more

Recommended publications
  • A Deep Learning Framework for Solar Phenomena Prediction
    FlareNet: A Deep Learning Framework for Solar Phenomena Prediction FDL 2017 Solar Storm Team: Sean McGregor1, Dattaraj Dhuri1,2, Anamaria Berea1,3, and Andrés Muñoz-Jaramillo1,4 1NASA’s 2017 Frontier Development Laboratory 2Tata Institute of Fundamental Research (TIFR), Mumbai, India 3Center for Complexity in Business, University of Maryland, College Park, MD, USA 4SouthWest Research Institute, Boulder, CO, USA Abstract Solar activity can interfere with the normal operation of GPS satellites, the power grid, and space operations, but inadequate predictive models mean we have little warning for the arrival of newly disruptive solar activity. Petabytes of data col- lected from satellite instruments aboard the Solar Dynamics Observatory (SDO) provide a high-cadence, high-resolution, and many-channeled dataset of solar phenomena. Several challenging deep learning problems may be derived from the data, including space weather forecasting (i.e., solar flares, solar energetic particles, and coronal mass ejections). This work introduces a software framework, FlareNet, for experimentation within these problems. FlareNet includes compo- nents for the downloading and management of SDO data, visualization, and rapid experimentation. The system architecture is built to enable collaboration between heliophysicists and machine learning researchers on the topics of image regres- sion, image classification, and image segmentation. We specifically highlight the problem of solar flare prediction and offer insights from preliminary experiments. 1 Introduction The violent release of solar magnetic energy – collectively referred to as “space weather" – is responsible for a variety of phenomena that can disrupt technological assets. In particular, solar flares (sudden brightenings of the solar corona) and coronal mass ejections (CMEs; the violent release of solar plasma) can disrupt long-distance communications, reduce Global Positioning System (GPS) accuracy, degrade satellites, and disrupt the power grid [5].
    [Show full text]
  • Multi-Spacecraft Analysis of the Solar Coronal Plasma
    Multi-spacecraft analysis of the solar coronal plasma Von der Fakultät für Elektrotechnik, Informationstechnik, Physik der Technischen Universität Carolo-Wilhelmina zu Braunschweig zur Erlangung des Grades einer Doktorin der Naturwissenschaften (Dr. rer. nat.) genehmigte Dissertation von Iulia Ana Maria Chifu aus Bukarest, Rumänien eingereicht am: 11.02.2015 Disputation am: 07.05.2015 1. Referent: Prof. Dr. Sami K. Solanki 2. Referent: Prof. Dr. Karl-Heinz Glassmeier Druckjahr: 2016 Bibliografische Information der Deutschen Nationalbibliothek Die Deutsche Nationalbibliothek verzeichnet diese Publikation in der Deutschen Nationalbibliografie; detaillierte bibliografische Daten sind im Internet über http://dnb.d-nb.de abrufbar. Dissertation an der Technischen Universität Braunschweig, Fakultät für Elektrotechnik, Informationstechnik, Physik ISBN uni-edition GmbH 2016 http://www.uni-edition.de © Iulia Ana Maria Chifu This work is distributed under a Creative Commons Attribution 3.0 License Printed in Germany Vorveröffentlichung der Dissertation Teilergebnisse aus dieser Arbeit wurden mit Genehmigung der Fakultät für Elektrotech- nik, Informationstechnik, Physik, vertreten durch den Mentor der Arbeit, in folgenden Beiträgen vorab veröffentlicht: Publikationen • Mierla, M., Chifu, I., Inhester, B., Rodriguez, L., Zhukov, A., 2011, Low polarised emission from the core of coronal mass ejections, Astronomy and Astrophysics, 530, L1 • Chifu, I., Inhester, B., Mierla, M., Chifu, V., Wiegelmann, T., 2012, First 4D Recon- struction of an Eruptive Prominence
    [Show full text]
  • The 2015 Senior Review of the Heliophysics Operating Missions
    The 2015 Senior Review of the Heliophysics Operating Missions June 11, 2015 Submitted to: Steven Clarke, Director Heliophysics Division, Science Mission Directorate Jeffrey Hayes, Program Executive for Missions Operations and Data Analysis Submitted by the 2015 Heliophysics Senior Review panel: Arthur Poland (Chair), Luca Bertello, Paul Evenson, Silvano Fineschi, Maura Hagan, Charles Holmes, Randy Jokipii, Farzad Kamalabadi, KD Leka, Ian Mann, Robert McCoy, Merav Opher, Christopher Owen, Alexei Pevtsov, Markus Rapp, Phil Richards, Rodney Viereck, Nicole Vilmer. i Executive Summary The 2015 Heliophysics Senior Review panel undertook a review of 15 missions currently in operation in April 2015. The panel found that all the missions continue to produce science that is highly valuable to the scientific community and that they are an excellent investment by the public that funds them. At the top level, the panel finds: • NASA’s Heliophysics Division has an excellent fleet of spacecraft to study the Sun, heliosphere, geospace, and the interaction between the solar system and interstellar space as a connected system. The extended missions collectively contribute to all three of the overarching objectives of the Heliophysics Division. o Understand the changing flow of energy and matter throughout the Sun, Heliosphere, and Planetary Environments. o Explore the fundamental physical processes of space plasma systems. o Define the origins and societal impacts of variability in the Earth/Sun System. • All the missions reviewed here are needed in order to study this connected system. • Progress in the collection of high quality data and in the application of these data to computer models to better understand the physics has been exceptional.
    [Show full text]
  • Introduction to the Physics of Solar Eruptions and Their Space Weather Impact
    Introduction to the physics of solar eruptions and their rsta.royalsocietypublishing.org space weather impact Vasilis Archontis1 and Loukas Vlahos2 Research 1 St Andrews University, School of Mathematics and Statistics, St Andrews KY 16 9SS, UK Article submitted to journal 2 Department of Physics, Aristotle University, 54124 Thessaloniki, Greece Subject Areas: Astrophysics, Plasma Physics, Space The physical processes, which drive powerful solar Weather eruptions, play an important role in our understanding of the Sun-Earth connection. In this Special Issue, we Keywords: firstly discuss how magnetic fields emerge from the Sun, magnetic fields, Coronal Mass solar interior to the solar surface, to build up active regions, which commonly host large-scale coronal Ejections disturbances, such as coronal mass ejections (CMEs). Then, we discuss the physical processes associated Author for correspondence: with the driving and triggering of these eruptions, the V. Archontis propagation of the large-scale magnetic disturbances e-mail: [email protected] through interplanetary space and the interaction of CMEs with Earth’s magnetic field. The acceleration mechanisms for the solar energetic particles related to explosive phenomena (e.g. flares and/or CMEs) in the solar corona are also discussed. The main aim of this Issue, therefore, is to encapsulate the present state- of-the-art in research related to the genesis of solar eruptions and their space-weather implications. This article is part of the theme issue ”Solar eruptions and their space weather impact”. arXiv:1905.08361v1 [astro-ph.SR] 20 May 2019 c The Authors. Published by the Royal Society under the terms of the Creative Commons Attribution License http://creativecommons.org/licenses/ by/4.0/, which permits unrestricted use, provided the original author and source are credited.
    [Show full text]
  • Supplemental Science Materials for Grades 5
    Effects of the Sun on Our Planet Supplemental science materials for grades 5 - 8 These supplemental curriculum materials are sponsored by the Stanford SOLAR (Solar On-Line Activity Resources) Center. In conjunction with NASA and the Learning Technologies Channel. Susanne Ashby Curriculum Specialist Paul Mortfield Solar Astronomers Todd Hoeksema Amberlee Chaussee Page Layout and Design Table of Contents Teacher Overview Objectives Science Concepts Correlation to the National Science Standards Segment Content/On-line Component Review Materials List Explorations Science Explorations • Sunlight and Plant Life • Life in a Greenhouse • Evaporation: How fast? • Evaporation (the Sequel): Where does the water go? • Now We’re Cookin’! • What I Can Do with Solar Energy • Riding a Radio Wave Career Explorations • Solar Scientist Answer Keys • Student Worksheet: Sunlight for Our Life • Science Exploration Guidesheet: Sunlight and Plant Life • Plant Observation Chart • Science Exploration Guidesheet: Life in a Greenhouse • Science Exploration Guidesheet: Evaporation: How fast? • Science Exploration Guidesheet: Evaporation: Where does the water go? • Science Exploration Guidesheet: Now We’re Cookin’! • Science Exploration Guidesheet: What I Can Do With Solar Energy • Science Exploration Guidesheet: Riding a Radio Wave Student Handouts • Student Reading: Sunlight for Our Life • Student Worksheet: Sunlight for Our Life • Science Exploration Guidesheet: (Generic form) • Riding a Radio Wave: Observation Graph • Career Exploration Guidesheet: Solar Scientist Appendix • Solar Glossary • Web Work 3 • Teacher Overview • Objectives • Science Concepts • Correlation to the National Science Standards • Segment Content/On-line Component Review • Materials List Teacher Overview Objectives • Students will observe how technology (through a greenhouse and photovoltaic cells) can enhance the solar energy Earth receives. • Students will observe how the sun’s radiant energy causes evaporation.
    [Show full text]
  • Heliospheric Data Center for Space Weather ALTEC and Oato – INAF Collaboration
    Heliospheric Data Center for Space Weather ALTEC and OATo – INAF collaboration ALTEC – Aerospace Logistics INAF – Italian National OATo – Turin Astro- All rights reserved © 2017 -2017 © reserved rights All Altec Technology Engineerig Company Astrophysics Institute physical Observatory www.altecspace.it Introduction Gaia-DPCT @ ALTEC Metis @ ALTEC Opsys All rights reserved © 2017 -2017 © reserved rights All Altec Following the excellent cooperation estabilished for Gaia Italian Data Processing Center, as well as Metis Coronagraph calibration and test campaign, ALTEC and OATo are joining efforts to create the Heliospheric Data Center as a key element of a Space Weather Data Center. www.altecspace.it Ref. Nr . Space Related Related Heliospheric Current Future Weather ALTEC Data Center OATo Activities Prospects Forecast Competences Competences All rights reserved © 2017 -2017 © reserved rights All Altec Page 3 www.altecspace.it Ref. Nr . Space Weather Forecast Among other methods ALTEC/OATo focus on forecast by means of space observations of the outer solar corona and heliosphere Identification of ejections of magnetic clouds, reaching the Earth magnetosphere ° Long-term forecast (days) with coronal observations, ° Short-term forecast (hours) with in situ heliospheric obs at L1 All rights reserved © 2017 -2017 © reserved rights All Altec Solar wind structure also allows predictions, days in advance, of minor geo-magnetic storm. www.altecspace.it Ref. Nr . Space Related Related Heliospheric Current Future Weather ALTEC Data Center OATo Activities Prospects Forecast Competences Competences All rights reserved © 2017 -2017 © reserved rights All Altec Page 5 www.altecspace.it Ref. Nr . Objectives And Approach Objectives ° Consolidate and evolve the Heliospheric Data Center , initially set up with the SOHO data coming from the ESA approved SOLAR (SOho Long-term ARchive) archive , in order to manage additional solar archives storing solar coronal and heliospheric data coming from ESA and NASA space programs.
    [Show full text]
  • Particles and Fields in the Interplanetary Medium M
    PARTICLES AND FIELDS IN THE INTERPLANETARY MEDIUM By KENNETH G. -MCCRACKEN UNIVERSITY OF ADELAIDE, ADELAIDE, AUSTRALIA M\Ian's knowledge of the properties of interplanetary space has advanced radically since 1962, the major part of this advance occurring since the commencement of the International Years of the Quiet Sun. The IQSY has, in fact, been quite unique in that it has seen the augmentation of the extensive synoptic studies of both geo- physical and solar phenomena such as were mounted during the IGY and its predecessors, the Polar Years of 1882 and 1932, by essentially continuous in situ studies of the interplanetary medium by detectors flown on interplanetary space- craft. Thus, since late 1963, no less than ten interplanetary spacecraft belonging to the Interplanetary -Monitoring Platform (DIP), Eccentric Geophysical Observa- tory (EGO), -Mariner, Pioneer, and Zond series have provided almost continuous surveillance of interplanetary phenomena, using second- and third-genleration detection devices. The fact that most of these spacecraft have made simultaneous measurements of a nIumber of the properties of the interplanetary medium has provided detailed information on the causal relationships between the several interplanetary parameters and geophysical phenomena, at a tinme when the relative lack of solar activity resulted in an attractive simplicity in the observed data. As' a consequence, the IQSY has provided an unprecedented series of observations of the causal relationships between solar, interplanetary, and geophysical phenomena, which will be of major importance in understanding the more complicated situations observed during periods of appreciable solar activity. In this review, I attempt to summarize the 1967 understanding of the interplanetary medium, this under- standing being based very heavily on work performed during and since the IQSY.
    [Show full text]
  • Sun – Part 23 - Solar Cycle 2
    Sun – Part 23 - Solar cycle 2 Sunspot cycle 11 year solar cycle Solar cycle in ultraviolet Related solar phenomena Various phenomena follow the solar cycle, including sunspots and coronal mass ejections (CME). As stated in Part 1, it is the number of sunspots which identifies the stages of the solar cycle. Sunspot positions also vary across the cycle. As each cycle begins, sunspots appear at mid-latitudes and then closer to the equator until solar maximum. They are almost never seen lower than 5° or higher than 40° North or South. There is a direct relationship between the solar cycle and solar luminosity. The photosphere radiates more actively when there are large sunspot numbers eg during maximum, although the presence of large groups can decrease luminosity for several days as they rotate across Earth's view. Solar irradiance output can increase by about 0.07% during maximum. The numbers of eruptions of solar flares and CMEs are also higher during solar maximum than minimum. Large CMEs occur, on average, a few times a day at maximum but down to one every few days at minimum. The size of these events, however, does not depend on the phase of the solar cycle; large flares can occur near solar minimum. While magnetic field changes are concentrated at sunspots, the whole Sun undergoes changes during the solar cycle, albeit of small magnitude. Other solar cycles Cyclical solar activity with much longer periods have been proposed eg 210 year Suess cycle, 2,300 year Hallstatt cycle, an unnamed 6,000 year cycle. Carbon-14 analysis has also identified cycles of 105, 131, 232, 395, 504, 805 and 2,241 years, possibly matching cycles derived from other sources.
    [Show full text]
  • Remote Sensing of the Heliospheric Solar Wind Using Radio Astronomy Methods and Numerical Simulations
    J. Astrophys. Astr. (2000) 21, 439–444 Remote Sensing of the Heliospheric Solar Wind using Radio Astronomy Methods and Numerical Simulations S. Ananthakrishnan, National Center for Radio Astrophysics, Tata Institute of Fundamental Research, Pune, India Abstract. The ground-based radio astronomy method of interplanetary scintillations (IPS) and spacecraft observations have shown, in the past 25 years, that while coronal holes give rise to stable, reclining high speed solar wind streams during the minimum of the solar activity cycle, the slow speed wind seen more during the solar maximum activity is better associated with the closed field regions, which also give rise to solar flares and coronal mass ejections (CME’s). The latter events increase signifi- cantly, as the cycle maximum takes place. We have recently shown that in the case of energetic flares one may be able to track the associated disturbances almost on a one to one basis from a distance of 0.2 to 1 AU using IPS methods. Time dependent 3D MHD models which are con- strained by IPS observations are being developed. These models are able to simulate general features of the solar-generated disturbances. Advances in this direction may lead to prediction of heliospheric propagation of these disturbances throughout the solar system. Key words. Sun—heliosphere, solar wind. 1. Introduction More than 20 years ago we made a detailed analysis of interplanetary scintillation (IPS) data from the 3 station radio observatory in San Diego and showed how the solar wind changes with the solar cycle (Coles et al. 1980). In particular we noted that solar phenomena are ‘intimately linked to the solar magnetic fields, which exhibit complex but systematic variations’.
    [Show full text]
  • Cosmic-Ray Transport in the Heliosphere
    Cosmic-Ray Transport in the Heliosphere J. Giacalone University of Arizona Heliophysics Summer School, Boulder, CO, July 16, 2013 TexPoint fonts used in EMF. Read the TexPoint manual before you delete this box.: A Outline • Lecture 1: Background • The heliosphere • Cosmic Rays in the heliosphere • Record-intensity cosmic rays during the last sunspot minimum • Has Voyager 1 entered the interstellar medium? • Lecture 2: Basic theory of charged-parJcle transport • Equaons of moJon, large-scale driMs, resonances • Restricted moJons • Diffusion, ConvecJon, Energy Change • The Parker transport equaon • Recitaon/Problem Sets: Applicaons As the Sun moves through its local environment, it carves out a region –the heliosphere – that is analogous to astrospheres seen surrounding other stars Parker’s view of the heliosphere in 1961 – from an analyJc formulaon. He came up with a scale of 45-90 AU from knowledge of the ram pressure at 1 AU and the esJmated interstellar pressure of (1-4) x 10-12 erg/cm2. • The solar wind flows supersonically and nearly radially from the Sun • Thus, its large-scale structure is determined mainly by the iniJal and boundary condiJons at the Sun. • The solar wind terminates at the terminaon shock – where 2 2 2 ρ Vw =ρ0 (r0/r) Vw = Pism. An instrucJve analog The Heliosphere (it may be here?) Heliosheath Terminaon Shock (outer) (inner) Voyager 1 Supersonic solar wind Voyager 2 Bow Shock ? Heliopause Why we study the outer heliosphere • The heliosphere represents the first of several boundaries shielding Earth from radiaon coming outside our solar system – it is important to understand how it does this (especially if we really want to send humans to Mars or the moon, or elsewhere) • NASA has several missions aimed at understanding the heliosphere (Voyager, IBEX, ACE, Ulysses, etc.) with rich data sets open for interpretaon.
    [Show full text]
  • Solar Flares: the Onset of Am Gnetic Reconnection and the Structure of Radiative Slow-Mode Shocks Peng Xu University of New Hampshire, Durham
    University of New Hampshire University of New Hampshire Scholars' Repository Doctoral Dissertations Student Scholarship Spring 1992 Solar flares: The onset of am gnetic reconnection and the structure of radiative slow-mode shocks Peng Xu University of New Hampshire, Durham Follow this and additional works at: https://scholars.unh.edu/dissertation Recommended Citation Xu, Peng, "Solar flares: The onset of magnetic reconnection and the structure of radiative slow-mode shocks" (1992). Doctoral Dissertations. 1693. https://scholars.unh.edu/dissertation/1693 This Dissertation is brought to you for free and open access by the Student Scholarship at University of New Hampshire Scholars' Repository. It has been accepted for inclusion in Doctoral Dissertations by an authorized administrator of University of New Hampshire Scholars' Repository. For more information, please contact [email protected]. INFORMATION TO USERS This manuscript has been reproduced from the microfilm master. UMI films the text directly from the original or copy submitted. Thus, some thesis and dissertation copies are in typewriter face, while others may be from any type of computer printer. The quality of this reproduction is dependent upon the quality of the copy submitted. Broken or indistinct print, colored or poor quality illustrations and photographs, print bleedthrough, substandard margins, and improper alignment can adversely affect reproduction. In the unlikely event that the author did not send UMI a complete manuscript and there are missing pages, these will be noted. Also, if unauthorized copyright material had to be removed, a note, will indicate the deletion. Oversize materials (e.g., maps, drawings, charts) are reproduced by sectioning the original, beginning at the upper left-hand corner and continuing from left to right in equal sections with small overlaps.
    [Show full text]
  • The Physical Character of the Sun
    Journal of the Minnesota Academy of Science Volume 2 Number 4 Article 6 1883 The Physical Character of the Sun J. F. Downey Follow this and additional works at: https://digitalcommons.morris.umn.edu/jmas Part of the The Sun and the Solar System Commons Recommended Citation Downey, J. F. (1883). The Physical Character of the Sun. Journal of the Minnesota Academy of Science, Vol. 2 No.4, 315-333. Retrieved from https://digitalcommons.morris.umn.edu/jmas/vol2/iss4/6 This Article is brought to you for free and open access by the Journals at University of Minnesota Morris Digital Well. It has been accepted for inclusion in Journal of the Minnesota Academy of Science by an authorized editor of University of Minnesota Morris Digital Well. For more information, please contact [email protected]. THE PHYSICAL CHARACTER OF THE SUN. BY PROF. J . F. DOWNEY, OF THE UNIVERSITY OF MINNESOTA. The objeot of this paper is~ give a brief review of what, at the present day, is known of the physioal oharacter of the s.un. On account of its far surpassing all other bodies in splendor, and its being the immediate souroe of our light and heat, it has always possessed more interest for man than has any ot4er celestial object. We could live .without the stars, without the moon, without the other planets; but without the sun, the world would at onoe realize Byron's terrible dream: " The ley earth Swung blind and blackening ln the moonless air; Morn came and wentr-and came, and brought no, day; And men forgot their passions, ln the dread Of their dessola~lon ; and all hearts Were chllled into a selftsh prayer for light." Before the invention of the telescope men could trace the apparent path of the sun among the stars, measure the inolination of that path with the equator, locate the points of crossing, and determine the time to oomplete one circuit; but they could learn nothing in regard to its physical constitution.
    [Show full text]