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Differential Magnetic Field Shear in an Active RegionThe three-dimensional extrapolation of magnetic field lines from a magnetogram obtained at Kitt Peak allows us to understand the global structure of the NOAA active region 6718, as observed in X-rays with the Normal Incidence X-ray Telescope (NIXT) and in Ha with the Multichannel Subtractive Double Pass spectrograph (MSDP) in Meudon on 1991 July 11. This active region was in a quiet stage. Bright X-ray loops connect plages having field strengths of approx. 300 G, while H-alpha fibriles connect penumbrae having strong spot fields to the surrounding network. Small, intense X-ray features in the moat region around a large spot, which could be called X-ray-bright points, are due mainly to the emergence of magnetic flux and merging of these fields with surrounding ones. A set of large-scale, sheared X-ray loops is observed in the central part of the active region. Based on the fit between the observed coronal structure and the field configurations (and assuming a linear force-free field), we propose a differential magnetic field shear model for this active region. The decreasing shear in outer portions of the active region may indicate a continual relaxation of the magnetic field to a lower energy state in the progressively older portions of the AR.
Document ID
19970017231
Acquisition Source
Headquarters
Document Type
Reprint (Version printed in journal)
Authors
Schmeider, B.
(Observatoire de Paris-Meudon France)
DeMoulin, P.
(Observatoire de Paris-Meudon France)
Aulanier, G.
(Observatoire de Paris-Meudon France)
Golub, Leon
(Smithsonian Astrophysical Observatory Cambridge, MA United States)
Date Acquired
September 8, 2013
Publication Date
April 1, 1997
Publication Information
Publication: Structure and Dynamics of Coronal Plasmas
Publisher: American Astronumical Society
Subject Category
Solar Physics
Accession Number
97N19591
Funding Number(s)
CONTRACT_GRANT: NAGw-4081
Distribution Limits
Public
Copyright
Public Use Permitted.
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