Coronal mass ejections are not coherent magnetohydrodynamic structures

Abstract Coronal mass ejections (CMEs) are episodic eruptions of solar plasma and magnetic flux that travel out through the solar system, driving extreme space weather. Interpretation of CME observations and their interaction with the solar wind typically assumes CMEs are coherent, almost solid-like...

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Autores principales:	M. J. Owens, M. Lockwood, L. A. Barnard
Formato:	article
Lenguaje:	EN
Publicado:	Nature Portfolio 2017
Materias:	Medicine R Science Q
Acceso en línea:	https://doaj.org/article/8144735b567844589c78e0b82a65e3ff
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spelling	oai:doaj.org-article:8144735b567844589c78e0b82a65e3ff2021-12-02T11:40:14ZCoronal mass ejections are not coherent magnetohydrodynamic structures10.1038/s41598-017-04546-32045-2322https://doaj.org/article/8144735b567844589c78e0b82a65e3ff2017-06-01T00:00:00Zhttps://doi.org/10.1038/s41598-017-04546-3https://doaj.org/toc/2045-2322Abstract Coronal mass ejections (CMEs) are episodic eruptions of solar plasma and magnetic flux that travel out through the solar system, driving extreme space weather. Interpretation of CME observations and their interaction with the solar wind typically assumes CMEs are coherent, almost solid-like objects. We show that supersonic radial propagation of CMEs away from the Sun results in geometric expansion of CME plasma parcels at a speed faster than the local wave speed. Thus information cannot propagate across the CME. Comparing our results with observed properties of over 400 CMEs, we show that CMEs cease to be coherent magnetohydrodynamic structures within 0.3 AU of the Sun. This suggests Earth-directed CMEs are less like billiard balls and more like dust clouds, with apparent coherence only due to similar initial conditions and quasi homogeneity of the medium through which they travel. The incoherence of CMEs suggests interpretation of CME observations requires accurate reconstruction of the ambient solar wind with which they interact, and that simple assumptions about the shape of the CMEs are likely to be invalid when significant spatial/temporal gradients in ambient solar wind conditions are present.M. J. OwensM. LockwoodL. A. BarnardNature PortfolioarticleMedicineRScienceQENScientific Reports, Vol 7, Iss 1, Pp 1-6 (2017)
institution	DOAJ
collection	DOAJ
language	EN
topic	Medicine R Science Q
spellingShingle	Medicine R Science Q M. J. Owens M. Lockwood L. A. Barnard Coronal mass ejections are not coherent magnetohydrodynamic structures
description	Abstract Coronal mass ejections (CMEs) are episodic eruptions of solar plasma and magnetic flux that travel out through the solar system, driving extreme space weather. Interpretation of CME observations and their interaction with the solar wind typically assumes CMEs are coherent, almost solid-like objects. We show that supersonic radial propagation of CMEs away from the Sun results in geometric expansion of CME plasma parcels at a speed faster than the local wave speed. Thus information cannot propagate across the CME. Comparing our results with observed properties of over 400 CMEs, we show that CMEs cease to be coherent magnetohydrodynamic structures within 0.3 AU of the Sun. This suggests Earth-directed CMEs are less like billiard balls and more like dust clouds, with apparent coherence only due to similar initial conditions and quasi homogeneity of the medium through which they travel. The incoherence of CMEs suggests interpretation of CME observations requires accurate reconstruction of the ambient solar wind with which they interact, and that simple assumptions about the shape of the CMEs are likely to be invalid when significant spatial/temporal gradients in ambient solar wind conditions are present.
format	article
author	M. J. Owens M. Lockwood L. A. Barnard
author_facet	M. J. Owens M. Lockwood L. A. Barnard
author_sort	M. J. Owens
title	Coronal mass ejections are not coherent magnetohydrodynamic structures
title_short	Coronal mass ejections are not coherent magnetohydrodynamic structures
title_full	Coronal mass ejections are not coherent magnetohydrodynamic structures
title_fullStr	Coronal mass ejections are not coherent magnetohydrodynamic structures
title_full_unstemmed	Coronal mass ejections are not coherent magnetohydrodynamic structures
title_sort	coronal mass ejections are not coherent magnetohydrodynamic structures
publisher	Nature Portfolio
publishDate	2017
url	https://doaj.org/article/8144735b567844589c78e0b82a65e3ff
work_keys_str_mv	AT mjowens coronalmassejectionsarenotcoherentmagnetohydrodynamicstructures AT mlockwood coronalmassejectionsarenotcoherentmagnetohydrodynamicstructures AT labarnard coronalmassejectionsarenotcoherentmagnetohydrodynamicstructures
_version_	1718395655397834752

Coronal mass ejections are not coherent magnetohydrodynamic structures

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