The Pre-penumbral Magnetic Canopy in the Solar Atmosphere

Journal
Date Issued
2016
Author(s)
MacTaggart, David
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•
DOI
Description
We thank the referee for many valuable comments. Weacknowledge a Carnegie Trust Research Incentive Grant (Ref:70323) and SOLARNET (http://www.solarnet-east.eu), funded by the European Commissions FP7 CapacitiesProgramme under the grant agreement No. 312495. Computational resources were provided by the EPSRC funded ARCHIE-WeSt High Performance Computer (www.archie-west.ac.uk), EPSRC grant No. EP/K000586/1. This work was also supported by the Italian MIUR-PRIN grant 2012P2HRCRon The active Sun and its effects on Space and Earth climate and by Space WEather Italian COmmunity (SWICO) Research Program. The SDO/HMI data are courtesy of NASA/SDOandthe HMI science team.
Abstract
Penumbrae are the manifestation of magnetoconvection in highly inclined (to the vertical direction) magnetic field. The penumbra of a sunspot tends to form, initially, along the arc of the umbra antipodal to the main region of flux emergence. The question of how highly inclined magnetic field can concentrate along the antipodal curves of umbrae, at least initially, remains to be answered. Previous observational studies have suggested the existence of some form of overlying magnetic canopy that acts as the progenitor for penumbrae. We propose that such overlying magnetic canopies are a consequence of how the magnetic field emerges into the atmosphere and are, therefore, part of the emerging region. We show, through simulations of twisted flux tube emergence, that canopies of highly inclined magnetic field form preferentially at the required locations above the photosphere.
Funding(s)
Volume
831
Issue
1
Start page
L4
Uri
Url
Issn Identifier
0004-637X
Ads BibCode
2016ApJ...831L...4M
Rights
open.access
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