Coronal Loops: Observations and Modeling of Confined Plasma
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Coronal Structure of Pre-Main Sequence Stars
**FULL TITLE** ASP Conference Series, Vol. **VOLUME**, **YEAR OF PUBLICATION** **NAMES OF EDITORS** Coronal Structure of Pre-Main Sequence Stars Moira Jardine SUPA, School of Physics and Astronomy, North Haugh, St Andrews, Fife, KY16 9SS, UK Abstract. The study of pre-main sequence stellar coronae is undertaken in many different wavelength regimes, with apparently conflicting results. X-ray studies of T Tauri stars suggest the presence of loops with a range of sizes ranging from less than a stellar radius to 10 stellar radii. Some of these stars show a clear rotational modulation in X-rays, but many do not and indeed the nature of this emission and its dependence on stellar mass and rotation rate is still a matter of debate. Some component of it may come from the accretion shock, but the location and extent of the accretion funnels (inferred from optical and UV observations) is as much of a puzzle as the mass accretion rate that they carry. Mass and angular momentum are not only gained by the star in the process of accretion, but also lost in either jets or winds. Linking all these different features is the magnetic field. Recent observations suggest the presence of structure on many scales, with a complex, multipolar field on small scales near the surface co-existing with a much simpler field structure on the larger scales at which the stellar field may be linking onto a surrounding disk. Some recent models suggest that the open field lines which are responsible for carrying gas escaping in winds and jets may also be responsible for much of the infalling accretion flow. -
15 Stellar Winds
15 Stellar Winds Stan Owocki Bartol Research Institute, Department of Physics and Astronomy, University of Colorado, Newark, DE, USA 1IntroductionandBackground....................................... 737 2ObservationalDiagnosticsandInferredProperties....................... 740 2.1 Solar Corona and Wind ................................................ 740 2.2 Spectral Signatures of Dense Winds from Hot and Cool Stars ................. 742 2.2.1 Opacity and Optical Depth ............................................. 742 2.2.2 Doppler-Shi!ed Line Absorption ........................................ 744 2.2.3 Asymmetric P-Cygni Pro"les from Scattering Lines ......................... 745 2.2.4 Wind-Emission Lines .................................................. 748 2.2.5 Continuum Emission in Radio and Infrared ................................ 750 3GeneralEquationsandFormalismforStellarWindMassLoss.............. 751 3.1 Hydrostatic Equilibrium in the Atmospheric Base of Any Wind ............... 751 3.2 General Flow Conservation Equations .................................... 752 3.3 Steady, Spherically Symmetric Wind Expansion ............................ 753 3.4 Energy Requirements of a Spherical Wind Out#ow .......................... 753 4CoronalExpansionandSolarWind................................... 754 4.1 Reasons for Hot, Extended Corona ....................................... 754 4.1.1 $ermal Runaway from Density and Temperature Decline of Line-Cooling ...... 754 4.1.2 Coronal Heating with a Conductive $ermostat ........................... -
Coronal Loops in a Box: 3D Models of Their Internal Structure, Dynamics and Heating
EGU21-13091 https://doi.org/10.5194/egusphere-egu21-13091 EGU General Assembly 2021 © Author(s) 2021. This work is distributed under the Creative Commons Attribution 4.0 License. Coronal loops in a box: 3D models of their internal structure, dynamics and heating Cosima Breu, Hardi Peter, Robert Cameron, Sami Solanki, Pradeep Chitta, and Damien Przybylski Max Planck Institute for Solar System Research, Sun and Heliosphere, Germany ([email protected]) The corona of the Sun, and probably also of other stars, is built up by loops defined through the magnetic field. They vividly appear in solar observations in the extreme UV and X-rays. High- resolution observations show individual strands with diameters down to a few 100 km, and so far it remains open what defines these strands, in particular their width, and where the energy to heat them is generated. The aim of our study is to understand how the magnetic field couples the different layers of the solar atmosphere, how the energy generated by magnetoconvection is transported into the upper atmosphere and dissipated, and how this process determines the scales of observed bright strands in the loop. To this end, we conduct 3D resistive MHD simulations with the MURaM code. We include the effects of heat conduction, radiative transfer and optically thin radiative losses. We study an isolated coronal loop that is rooted with both footpoints in a shallow convection zone layer. To properly resolve the internal structure of the loop while limiting the size of the computational box, the coronal loop is modelled as a straightened magnetic flux tube. -
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 -
The High Resolution Camera
CXC Newsletter The High Resolution Camera To create a source catalog of the M31 center and search for time variability of the sources, we includ- Ralph Kraft, Hans Moritz Guenther (SAO), and ed 23 observations from November 1999 to February Wolfgang Pietsch (MPE) 2005 (adding about 250 ks exposure time). We detected 318 X-ray sources and created long term light curves It has been another quiet, but successful year for for all of them. We classified sources as highly variable HRC operations. The instrument performs well with or outbursting (with subclasses short vs. long outbursts no significant anomalies or instrumental issues. The and activity periods). 129 sources could be classified as HRC continues to be used for a wide variety of astro- X-ray binaries due to their position in globular clusters physical investigations. In this chapter, we briefly de- or their strong time variability (see Fig. 2). We detected scribe two such science studies. First, a collaboration seven supernova remnants, one of which is a new can- led by Dr. Wolfgang Pietsch of MPE used the HRC to didate, and also resolved the first X-rays from a known study the X-ray state of the nova population in M31 radio supernova remnant (see Hofmann et al. 2013). in conjunction with XMM-Newton and optical studies. In a second study, Guenther et al. used the HRC to They found that there is a strong correlation between determine the origin of the X-ray emission from β Pic, the optical and X-ray properties of these novae. Sec- a nearby star with a dusty disk. -
SKYLAB: a PROGRESS REPORT Abstract. the Skylab Apollo
SKYLAB: A PROGRESS REPORT R. M. MacQUEEN High Altitude Observatory, National Center for Atmospheric Research*, Boulder, Colo., U.S.A. (Presented by G. Newkirk) Abstract. The Skylab Apollo Telescope. Mount contains six principal instruments spanning the X-ray to visible wavelength range. These experiments include an exter nally occulted white light coronagraph from the High Altitude Observatory which observes the outer solar corona from 1.5 to 6.0 radii from Sun center, in broadband (3500-7000 A) white light with approximately 10" spatial resolution. An X-ray spectrographic telescope of the American Science and Engineering, Inc. employs six filters and an objective grating to observe a 48' field of view in the wavelength range 3.5-6.0 A, with approximately 3" spatial resolution. A scanning ultraviolet poly- chromator, spectroheliometer of the Harvard College Observatory is capable of observing 1.2 A spectral resolution from 300-1350 A with a 7 detector array. The field of view of the instrument is determined by its operational mode and ranges from 5' x 5' to 5" x 5". An X-ray telescope from the Marshall Space Flight Center employs five metal filters to observe the 5-33 A spectral region with 2.5" spatial resolution over the 40' field of view. The Naval Research Laboratory has supplied two instruments: the first, an XUV spectroheliograph, covers wavelength regions 150-335 A and 321-625 A, with somewhat better than 5" spatial resolution and a spectral resolution of 0.13 A (for a 10" feature). The second instrument, a slit spectrograph, covers the spectral range 970-3940 A in two bands, 970-1970 and 1940-3940, and has 0.5 and 0.1 A spectral resolution respectively, with a 2" x 60" slit. -
GSFC Heliophysics Science Division 2009 Science Highlights
NASA/TM–2010–215854 GSFC Heliophysics Science Division 2009 Science Highlights Holly R. Gilbert, Keith T. Strong, Julia L.R. Saba, and Yvonne M. Strong, Editors December 2009 Front Cover Caption: Heliophysics image highlights from 2009. For details of these images, see the key on Page v. The NASA STI Program Offi ce … in Profi le Since its founding, NASA has been ded i cated to the • CONFERENCE PUBLICATION. Collected ad vancement of aeronautics and space science. The pa pers from scientifi c and technical conferences, NASA Sci en tifi c and Technical Information (STI) symposia, sem i nars, or other meetings spon sored Pro gram Offi ce plays a key part in helping NASA or co spon sored by NASA. maintain this impor tant role. • SPECIAL PUBLICATION. Scientifi c, techni cal, The NASA STI Program Offi ce is operated by or historical information from NASA pro grams, Langley Research Center, the lead center for projects, and mission, often concerned with sub- NASAʼs scientifi c and technical infor ma tion. The jects having substan tial public interest. NASA STI Program Offi ce pro vides ac cess to the NASA STI Database, the largest collec tion of • TECHNICAL TRANSLATION. En glish-language aero nau ti cal and space science STI in the world. trans la tions of foreign scien tifi c and techni cal ma- The Pro gram Offi ce is also NASAʼs in sti tu tion al terial pertinent to NASAʼs mis sion. mecha nism for dis sem i nat ing the results of its research and devel op ment activ i ties. -
Why Is the Sun's Corona So Hot? Why Are Prominences So Cool?
Why is the Sun’s corona so hot? Why are prominences so cool? Jack B. Zirker and Oddbjørn Engvold Citation: Physics Today 70, 8, 36 (2017); doi: 10.1063/PT.3.3659 View online: http://dx.doi.org/10.1063/PT.3.3659 View Table of Contents: http://physicstoday.scitation.org/toc/pto/70/8 Published by the American Institute of Physics Why is the Sun’s corona so hot? Why are prominences so cool? Jack B. Zirker and Oddbjørn Engvold Over the past several decades, solar physicists have made steady progress in answering the COURTESY OF SHADIA HABBAL two long-standing questions, but puzzles remain. Jack Zirker is an astronomer emeritus at the National Solar Observatory’s facilities on Sacramento Peak in Sunspot, New Mexico. Oddbjørn Engvold is an emeritus professor at the University of Oslo’s Institute of Theoretical Astrophysics in Oslo, Norway. n the 21st of this month, millions of enthusiasts found between the x-ray brightness of active regions—hot plasma-filled in the US will be treated to a total eclipse of the aggregations of looped magnetic field Sun. During two minutes of darkness, they lines—and the strength of their surface will see—weather permitting—the extremely magnetic fields. That important clue O suggested that magnetic fields must faint outer atmosphere of the Sun, the corona. play an important role in heating the They may also see red feathery sheets of gas called prominences corona. In a parallel development, Eugene immersed in the corona. Parker predicted in 1958 that a hot co- rona must expand into space as a solar Since the 1940s astronomers have known that the corona is wind. -
Variability of a Stellar Corona on a Time Scale of Days Evidence for Abundance Fractionation in an Emerging Coronal Active Region
A&A 550, A22 (2013) Astronomy DOI: 10.1051/0004-6361/201220491 & c ESO 2013 Astrophysics Variability of a stellar corona on a time scale of days Evidence for abundance fractionation in an emerging coronal active region R. Nordon1,2,E.Behar3, and S. A. Drake4 1 Max-Planck-Institut für Extraterrestrische Physik (MPE), Postfach 1312 85741 Garching, Germany 2 School of Physics and Astronomy, The Raymond and Beverly Sackler Faculty of Exact Sciences, Tel-Aviv University, 69978 Tel-Aviv, Israel e-mail: [email protected] 3 Physics Department, Technion Israel Institute of Technology, 32000 Haifa, Israel e-mail: [email protected] 4 NASA/GSFC, Greenbelt, 20771 Maryland, USA e-mail: [email protected] Received 3 October 2012 / Accepted 1 December 2012 ABSTRACT Elemental abundance effects in active coronae have eluded our understanding for almost three decades, since the discovery of the first ionization potential (FIP) effect on the sun. The goal of this paper is to monitor the same coronal structures over a time interval of six days and resolve active regions on a stellar corona through rotational modulation. We report on four iso-phase X-ray spectroscopic observations of the RS CVn binary EI Eri with XMM-Newton, carried out approximately every two days, to match the rotation period of EI Eri. We present an analysis of the thermal and chemical structure of the EI Eri corona as it evolves over the six days. Although the corona is rather steady in its temperature distribution, the emission measure and FIP bias both vary and seem to be correlated. -
Ublic Affairs Office Eorge C. Marshall Space Flight Center Tional
ublic Affairs Office March 1, 1968 eorge C. Marshall Space Flight Center tional Aeronautics and Space Administration arshall Space Flight Center, Alabama Phone: 876-1102, 876 -1959 APOLLO TELESCOPE MOUNT \ -- Fact Sheet -- The Apollo Telescope Mount (ATM) is being developed to give space scientists a look at the sun's activity unencumbered by the fogging effects of the earth's atmosphere. The National Aeronautics and Space Administration plans to launch the first of its manned solar observatories, ATM-A, in 1971. The space agency is joined by the scientific community and industry in developing the highly sophisticated satellite. Five principal investigators, all experts in astronomy and solar physics, have designed five experiments for the first ATM flight. The eight instruments used in these five ATM experiments will obtain measurements of the sun in the extreme ultreme ultraviolet and X-ray portions of the electromagnetic spectrum which cannot penetrate the earth's atmosphere and obtain pictures of the sun's corona in the white light portion of the spectrum. Dr. George E. Mueller, NASA Associate Administrator for Manned Space Flight, has said the ATM "provides a new great capability for a variety of solar and stellar scientific experiments" to be performed above the atmosphere, where the sun and stars can be clearly observed without being obscured by the earth's AAP CLUSTER -- The Apollo Telescope Mount, shown at top, is one of the principal payloads in the first Apollo Applications flights. Other main elements are the Saturn I workshop, bottom, the airlock/multiple docking adapter and Apollo spacecraft. -2 - atmosphere. The first ATM, one of the early Apollo Applications missions, is a forerunner of more advanced manned solar and stellar observatories which will provide an increased data gathering capability for astronomers. -
19910023712.Pdf
SOLAR ASTRONOMY IX-1 Solar Astronomy 59-el N91-38026 Table of Contents 0. Executive Summary ................................ page 2 1. An Overview of Modern Solar Physics ......................... page 5 1.1 General Perspectives .............................. page 5 1.2 Frontiers and Goals for the 1990s ........................ page 8 1.2.1 The Solar Interior ............................ page 8 1.2.2 The Solar Surface ............................ page 9 1.2.3 The Outer Solar Atmosphere: Corona and Heliosphere ............ page 9 1.2.4 The Solar-Stellar Connection ....................... page 10 2. Ground-Based Solar Physics ............................. page 11 2.1 Introduction ................................. page 11 2.2 Status of Major Projects and Facilities ...................... page 11 2.3 A Prioritized Ground-based Program for the 1990s ................. page 12 2.3.1 Prerequisites .............................. page 12 2.3.2 Prioritization .............................. page 12 2.3.3 The Major Initiative: Solar Magnetohydrodynamics, and the LEST ....... page 12 2.3.3.1 The Large Earth-based Solar Telescope (LEST) ............ page 14 2.3.3.2 Infrared Facility Development .................... page 15 2.3.4 Moderate Initiatives ........................... page 15 2.3.5 Interdisciplinary Initiatives ........................ page 18 2.4 Conclusions and Summary ........................... page 20 3. Space Observations For Solar Physics ......................... page 20 3.1 Introduction ................................. page 20 3.2 -
National Solar Observatory
NATIONALSOLAROBSERVATORY NSO TUCSON, ARIZONA • SAC PEAK, NEW MEXICO From the NSO Director’s Office Steve Keil SO staff and several of our partners have been busy this generation bidimensional spectrometry instrument based on fall preparing a construction proposal for the Advanced a dual Fabry-Perot interferometric system. It combines high- Technology Solar Telescope (ATST). e proposal will be spectral resolution with short exposure times and a large field of Nsubmitted by the end of 2003 to comply with the National Science view, as well as the ability to work in polarized light. is will allow Foundation Major Research Equipment program schedule for a it to address a variety of observational programs in solar physics. potential startup in 2006. e proposal is based on the conceptual IBIS is one of the concepts under consideration for a visible light, design developed over the past few years that was reviewed at a narrowband filter for the ATST. It is currently fed by the low-order Conceptual Design Review in late August. adaptive optics system and can be used simultaneously with the horizontal spectrograph and other filter systems. A parallel effort to submit a proposal to the European Union (EU) to participate in the final stages of the design effort is being New data collection computers are being installed at the DST organized for the EU Sixth Framework Program. is will hopefully facility, and a data transfer system is being established to allow set the stage for later European participation in the telescope users to take the data home on the medium of their choice.