University of Oulu

Burtseva, O., Gosain, S., Pevtsov, A. (2017) Search for a Signature of Twist-removal in the Magnetic Field of Sunspots in Relation with Major Flares. Astrophysical Journal, 849 (2), 103.

Search for a signature of twist-removal in the magnetic field of sunspots in relation with major llares

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Author: Burtseva, Olga1; Gosain, Sanjay1; Pevtsov, Alexei A.1,2
Organizations: 1National Solar Observatory, Boulder, CO 80303, USA
2ReSoLVE Centre of Excellence, Space Climate research unit, 90014 University of Oulu, Finland
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 2.4 MB)
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Language: English
Published: IOP Publishing, 2017
Publish Date: 2019-03-05


We investigate the restructuring of the magnetic field in sunspots associated with two flares: the X6.5 flare on 2006 December 6 and the X2.2 flare on 2011 February 15. The observed changes were evaluated with respect to the so-called twist-removal model, in which helicity (twist) is removed from the corona as the result of an eruption. Since no vector magnetograms were available for the X6.5 flare, we applied the azimuthal symmetry approach to line-of-sight magnetograms to reconstruct the pseudo-vector magnetic field and investigate the changes in average twist and inclination of magnetic field in the sunspot around the time of the flare. For the X2.2 flare, results from the full vector magnetograms were compared with the pseudo-vector field data. For both flares, the data show changes consistent with the twist-removal scenario. We also evaluate the validity of the azimuthal symmetry approach on simple isolated round sunspots. In general, the derivations based on the azimuthal symmetry approach agree with true-vector field data though we find that even for symmetric sunspots the distribution of the magnetic field may deviate from an axially symmetric distribution.

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Series: Astrophysical journal
ISSN: 0004-637X
ISSN-E: 1538-4357
ISSN-L: 0004-637X
Volume: 849
Issue: 2
Article number: 103
DOI: 10.3847/1538-4357/aa8dfc
Type of Publication: A1 Journal article – refereed
Field of Science: 115 Astronomy and space science
Funding: Authors of this work are partially supported by NASA grant NNX14AE05G. A.A.P. acknowledges the financial support by the Academy of Finland to the ReSoLVE Centre of Excellence (project No. 272157).
Academy of Finland Grant Number: 272157
Detailed Information: 272157 (Academy of Finland Funding decision)
Copyright information: © 2017. The American Astronomical Society. All rights reserved