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The Formation and Maintenance of the Dominant Southern Polar Crown Cavity of Cycle 24In this article, we report a study of the longest-lived polar crown cavity of Solar Cycle 24, using an observation from 2013, and propose a physical mechanism to explain its sustained existence. We used high temporal and spatial resolution observations from the Atmospheric Imaging Assembly (AIA) and the Helioseismic Magnetic Imager (HMI) instruments on board the Solar Dynamics Observatory (SDO) to explore the structure and evolution of the cavity. Although it existed for more than a year, we examined the circumpolar cavity in great detail from 2013 March 21 to 2013 October 31. Our study reinforces the existing theory of formation of polar crown filaments that involves two basic processes to form any polar crown cavity as well as the long-lived cavity that we studied here. First, the underlying polarity inversion line (PIL) of the circumpolar cavity is formed between (1) the trailing part of dozens of decayed active regions distributed in different longitudes and (2) the unipolar magnetic field in the polar coronal hole. Second, the long life of the cavity is sustained by the continuing flux cancellation along the PIL. The flux is persistently transported toward the polar region through surface meridional flow and diffusion. The continuing flux cancellation leads to the shrinking of the polar coronal hole.
Document ID
20180000635
Acquisition Source
Goddard Space Flight Center
Document Type
Reprint (Version printed in journal)
Authors
Karna, N.
(George Mason Univ. Fairfax, VA, United States)
Zhang, J.
(George Mason Univ. Fairfax, VA, United States)
Pesnell, W. D.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Date Acquired
January 18, 2018
Publication Date
January 23, 2017
Publication Information
Publication: The Astrophysical Journal
Publisher: American Astronomical Society
Volume: 835
Issue: 2
ISSN: 2041-8205
e-ISSN: 2041-8213
Subject Category
Astrophysics
Solar Physics
Report/Patent Number
GSFC-E-DAA-TN51108
Funding Number(s)
CONTRACT_GRANT: NSF AGS-1460188
CONTRACT_GRANT: NSF AGS-1249270
Distribution Limits
Public
Copyright
Other

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