1. Highly structured slow solar wind emerging from an equatorial coronal hole
- Author
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Vladimir Krasnoselskikh, Säm Krucker, C. Fong, D. J. McComas, James A. Klimchuk, Tai Phan, Michel Moncuquet, N.-E. Raouafi, Marco Velli, Anthony W. Case, C. C. Chaston, Justin C. Kasper, John W. Bonnell, Melvyn L. Goldstein, David Burgess, John R. Wygant, Gregory G. Howes, Christopher H. K. Chen, Trevor A. Bowen, David Stansby, Robert E. Ergun, R. Laker, Samuel T. Badman, Stuart D. Bale, T. Dudok de Wit, F. S. Mozer, Robert J. MacDowall, Keith Goetz, David M. Malaspina, Nicole Meyer-Vernet, Jonathan Eastwood, Davin Larson, Katherine Goodrich, Michael L. Stevens, Adam Szabo, William M. Farrell, Marc Pulupa, Benjamin D. G. Chandran, Kelly E. Korreck, Paul J. Kellogg, Milan Maksimovic, James Drake, J. C. Martínez-Oliveros, Timothy S. Horbury, Cynthia A Cattell, T. Woolley, Chadi Salem, Peter Harvey, Space Sciences Laboratory [Berkeley] (SSL), University of California [Berkeley], University of California-University of California, Astronomy Unit [London] (AU), Queen Mary University of London (QMUL), School of Physics and Astronomy [Minneapolis], University of Minnesota [Twin Cities] (UMN), University of Minnesota System-University of Minnesota System, University of California, Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Laboratory for Atmospheric and Space Physics [Boulder] (LASP), University of Colorado [Boulder], Imperial College London, Harvard-Smithsonian Center for Astrophysics (CfA), Harvard University [Cambridge]-Smithsonian Institution, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Princeton University, NASA Ames Research Center (ARC), Smithsonian Astrophysical Observatory, Smithsonian Institution, The Leverhulme Trust, and Science and Technology Facilities Council (STFC)
- Subjects
Solar minimum ,010504 meteorology & atmospheric sciences ,General Science & Technology ,Astrophysics::High Energy Astrophysical Phenomena ,WAVES ,Astronomical unit ,Coronal hole ,Solar radius ,Astrophysics ,01 natural sciences ,INTERPLANETARY ,0103 physical sciences ,Astrophysics::Solar and Stellar Astrophysics ,010303 astronomy & astrophysics ,MISSION ,0105 earth and related environmental sciences ,Physics ,Science & Technology ,Multidisciplinary ,MAGNETIC-FIELD ,Ecliptic ,Solar physics ,Multidisciplinary Sciences ,MODEL ,Solar wind ,[SDU]Sciences of the Universe [physics] ,13. Climate action ,Physics::Space Physics ,Science & Technology - Other Topics ,Astrophysics::Earth and Planetary Astrophysics ,[PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph] ,Interplanetary spaceflight - Abstract
During the solar minimum, when the Sun is at its least active, the solar wind1,2 is observed at high latitudes as a predominantly fast (more than 500 kilometres per second), highly Alfvenic rarefied stream of plasma originating from deep within coronal holes. Closer to the ecliptic plane, the solar wind is interspersed with a more variable slow wind3 of less than 500 kilometres per second. The precise origins of the slow wind streams are less certain4; theories and observations suggest that they may originate at the tips of helmet streamers5,6, from interchange reconnection near coronal hole boundaries7,8, or within coronal holes with highly diverging magnetic fields9,10. The heating mechanism required to drive the solar wind is also unresolved, although candidate mechanisms include Alfven-wave turbulence11,12, heating by reconnection in nanoflares13, ion cyclotron wave heating14 and acceleration by thermal gradients1. At a distance of one astronomical unit, the wind is mixed and evolved, and therefore much of the diagnostic structure of these sources and processes has been lost. Here we present observations from the Parker Solar Probe15 at 36 to 54 solar radii that show evidence of slow Alfvenic solar wind emerging from a small equatorial coronal hole. The measured magnetic field exhibits patches of large, intermittent reversals that are associated with jets of plasma and enhanced Poynting flux and that are interspersed in a smoother and less turbulent flow with a near-radial magnetic field. Furthermore, plasma-wave measurements suggest the existence of electron and ion velocity-space micro-instabilities10,16 that are associated with plasma heating and thermalization processes. Our measurements suggest that there is an impulsive mechanism associated with solar-wind energization and that micro-instabilities play a part in heating, and we provide evidence that low-latitude coronal holes are a key source of the slow solar wind. Measurements from the Parker Solar Probe show that slow solar wind near the Sun’s equator originates in coronal holes.
- Published
- 2019