view Abstract Citations (91) References (29) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Differential Magnetic Field Shear in an Active Region Schmieder, B. ; Demoulin, P. ; Aulanier, G. ; Golub, L. Abstract The three-dimensional extrapolation of magnetic field lines from a magneto gram 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 Hα 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 ∼300 G, while Hα 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. Publication: The Astrophysical Journal Pub Date: August 1996 DOI: 10.1086/177662 Bibcode: 1996ApJ...467..881S Keywords: MAGNETOHYDRODYNAMICS: MHD; SUN: MAGNETIC FIELDS; SUN: FACULAE; PLAGES full text sources ADS |