Coronal Holes
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In this article, a review of the plasma properties in coronal holes and how these measurements are used to reveal details about the physical processes that heat the solar corona and accelerate the solar wind is presented.Abstract:
Coronal holes are the darkest and least active regions of the Sun, as observed both on the solar disk and above the solar limb. Coronal holes are associated with rapidly expanding open magnetic fields and the acceleration of the high-speed solar wind. This paper reviews measurements of the plasma properties in coronal holes and how these measurements are used to reveal details about the physical processes that heat the solar corona and accelerate the solar wind. It is still unknown to what extent the solar wind is fed by flux tubes that remain open (and are energized by footpoint-driven wave-like fluctuations), and to what extent much of the mass and energy is input intermittently from closed loops into the open-field regions. Evidence for both paradigms is summarized in this paper. Special emphasis is also given to spectroscopic and coronagraphic measurements that allow the highly dynamic non-equilibrium evolution of the plasma to be followed as the asymptotic conditions in interplanetary space are established in the extended corona. For example, the importance of kinetic plasma physics and turbulence in coronal holes has been affirmed by surprising measurements from UVCS that heavy ions are heated to hundreds of times the temperatures of protons and electrons. These observations point to specific kinds of collisionless Alfven wave damping (i.e., ion cyclotron resonance), but complete models do not yet exist. Despite our incomplete knowledge of the complex multi-scale plasma physics, however, much progress has been made toward the goal of understanding the mechanisms responsible for producing the observed properties of coronal holes.read more
Citations
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Journal ArticleDOI
Highly structured slow solar wind emerging from an equatorial coronal hole
Stuart D. Bale,Samuel T. Badman,John W. Bonnell,Trevor A. Bowen,David Burgess,Anthony W. Case,Cynthia A Cattell,Benjamin D. G. Chandran,C. C. Chaston,Christopher H. K. Chen,James Drake,T. Dudok de Wit,Jonathan Eastwood,Robert E. Ergun,William M. Farrell,C. Fong,Keith Goetz,Melvyn L. Goldstein,Melvyn L. Goldstein,Katherine Goodrich,Peter Harvey,Timothy S. Horbury,Gregory G. Howes,Justin C. Kasper,Justin C. Kasper,Paul J. Kellogg,James A. Klimchuk,Kelly E. Korreck,Vladimir Krasnoselskikh,Säm Krucker,Säm Krucker,R. Laker,Davin Larson,Robert J. MacDowall,Milan Maksimovic,David M. Malaspina,J. C. Martínez-Oliveros,D. J. McComas,Nicole Meyer-Vernet,Michel Moncuquet,F. S. Mozer,Tai Phan,Marc Pulupa,N.-E. Raouafi,Chadi Salem,David Stansby,Michael L. Stevens,Adam Szabo,Marco Velli,T. Woolley,John R. Wygant +50 more
TL;DR: Measurements from the Parker Solar Probe show that slow solar wind near the Sun’s equator originates in coronal holes, and plasma-wave measurements suggest the existence of electron and ion velocity-space micro-instabilities that are associated with plasma heating and thermalization processes.
Journal ArticleDOI
Prevalence of small-scale jets from the networks of the solar transition region and chromosphere
Hui Tian,Edward E. DeLuca,Steven R. Cranmer,B. De Pontieu,Hardi Peter,Juan Martinez-Sykora,L. Golub,Sean McKillop,Katharine K. Reeves,M. P. Miralles,Patrick I. McCauley,Steven H. Saar,Paola Testa,M. Weber,Nicholas A. Murphy,James R. Lemen,A. M. Title,Paul Boerner,Neal E. Hurlburt,T. D. Tarbell,Jean-Pierre Wuelser,Lucia Kleint,Charles C. Kankelborg,S. Jaeggli,Mats Carlsson,Viggo Hansteen,Scott W. McIntosh +26 more
TL;DR: In this article, the authors used the Interface Region Imaging Spectrograph (IRIS) to detect small-scale jets with speeds of 80 to 250 kilometers per second from the narrow bright network lanes of this interface region.
Journal ArticleDOI
The FIP and Inverse FIP Effects in Solar and Stellar Coronae
TL;DR: In this article, the first ionization potential (FIP) effect was observed in the solar corona and slow-speed wind, and in the coronae of solar-like dwarf stars, and the "inverse FIP" effect seen in the corona of stars of later spectral type; specifically M dwarfs.
Journal ArticleDOI
Magnetism, dynamo action and the solar-stellar connection
TL;DR: Observations and theory of magnetism in the Sun and other stars are reviewed, with a partial focus on the “Solar-stellar connection”: ways in which studies of other stars have influenced the authors' understanding of theSun and vice versa.
Journal ArticleDOI
Solar wind stream interaction regions throughout the heliosphere
TL;DR: This paper focuses on the interactions between the fast solar wind from coronal holes and the intervening slower solar wind, leading to the creation of stream interaction regions that corotate with the Sun and may persist for many solar rotations.
References
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