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Title: Study of Three-dimensional Magnetic Structure and the Successive Eruptive Nature of Active Region 12371
Authors: Vemareddy, P
Demoulin, P
Keywords: Sun: corona;Sun: coronal mass ejections (CMEs);Sun: evolution;Sun: filaments, prominences;Sun: flares;Sun: magnetic fields
Issue Date: 20-Apr-2018
Publisher: IOP Publishing
Citation: The Astrophysical Journal, Vol. 857, No. 2, 90
Abstract: We study the magnetic structure of a successively erupting sigmoid in active region 12371 by modeling the quasi-static coronal field evolution with nonlinear force-free field (NLFFF) equilibria. Helioseismic and Magnetic Imager/Solar Dynamic Observatory vector magnetograms are used as input to the NLFFF model. In all eruption events, the modeled structure resembles the observed pre-eruptive coronal sigmoid and the NLFFF core field is a combination of double inverse-J-shaped and inverse-S field lines with dips touching the photosphere. Such field lines are formed by the flux cancellation reconnection of opposite-J field lines at bald-patch locations, which in turn implies the formation of a weakly twisted flux-rope (FR) from large-scale sheared arcade field lines. Later on, this FR undergoes coronal tether-cutting reconnection until a coronal mass ejection is triggered. The modeled structure captured these major features of sigmoid-to-arcade-to-sigmoid transformation, which is reoccuring under continuous photospheric flux motions. Calculations of the field line twist reveal a fractional increase followed by a decrease of the number of pixels having a range of twist. This traces the buildup process of a twisted core field by slow photospheric motions and the relaxation after eruption, respectively. Our study infers that the large eruptivity of this AR is due to a steep decrease of the background coronal field meeting the torus instability criteria at a low height (≈40 Mm) in contrast to noneruptive ARs.
Description: Restricted Access
ISSN: 0004-637X
???metadata.dc.rights???: © The American Astronomical Society
Appears in Collections:IIAP Publications

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