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Converging Supergranular Flows and the Formation of Coronal PlumesEarlier studies have suggested that coronal plumes are energized by magnetic reconnection between unipolar flux concentrations and nearby bipoles, even though magnetograms sometimes show very little minority-polarity flux near the footpoints of plumes. Here we use high-resolution extreme-ultraviolet (EUV) images and magnetograms from the Solar Dynamics Observatory (SDO) to clarify the relationship between plume emission and the underlying photospheric field. We find that plumes form where unipolar network elements inside coronal holes converge to form dense clumps, and fade as the clumps disperse again. The converging flows also carry internetwork fields of both polarities. Although the minority-polarity flux is sometimes barely visible in the magnetograms, the corresponding EUV images almost invariably show loop-like features in the core of the plumes, with the fine structure changing on timescales of minutes or less. We conclude that the SDO observations are consistent with a model in which plume emission originates from interchange reconnection in converging flows, with the plume lifetime being determined by the approximately 1-day evolutionary timescale of the supergranular network. Furthermore, the presence of large EUV bright points and/or ephemeral regions is not a necessary precondition for the formation of plumes, which can be energized even by the weak, mixed-polarity internetwork fields swept up by converging flows.
Document ID
20160007924
Acquisition Source
Goddard Space Flight Center
Document Type
Reprint (Version printed in journal)
Authors
Wang, Y.-M.
(Naval Research Lab. Washington, DC, United States)
Warren, H. P.
(Naval Research Lab. Washington, DC, United States)
Muglach, K.
(Science Collaborator)
Date Acquired
June 27, 2016
Publication Date
February 22, 2016
Publication Information
Publication: The Astrophysical Journal
Publisher: AAS PUBLICATIONS
Volume: 818
Issue: 2
Subject Category
Solar Physics
Report/Patent Number
GSFC-E-DAA-TN33266
Distribution Limits
Public
Copyright
Other
Keywords
Sun: corona
Sun: magnetic fields
Sun: UV radiation

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