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Magnetohydrostatic modeling of the solar atmosphere

Science China(Technological Sciences) 2022年第8期65卷 1710-1726页

作者： ZHU XiaoShuai NEUKIRCH thomas wiegelmann thomas State Key Laboratory of Space Weather National Space Science CenterChinese Academy of SciencesBeijing 100190China National Astronomical Observatories Chinese Academy of SciencesBeijing 100101China School of Mathematics and Statistics University of St AndrewsSt Andrews KY169SSUK Max-Planck-Institut f¨ur Sonnensystemforschung G¨ottingen 37077Germany

Understanding structures and evolutions of the magnetic fields and plasma in multiple layers on the Sun is very important. A force-free magnetic field which is an accurate approximation of the solar corona due to the low plasma β has been widely studied and used to model the coronal magnetic structure. While the force-freeness assumption is well satisfied in the solar corona, the lower atmosphere is not force-free given the high plasma β. Therefore, a magnetohydrostatic(MHS) equilibrium which takes into account plasma forces, such as pressure gradient and gravitational force, is considered to be more appropriate to describe the lower atmosphere. This paper reviews both analytical and numerical extrapolation methods based on the MHS assumption for calculating the magnetic fields and plasma in the solar atmosphere from measured magnetograms.

关键词： magnetic field photosphere chromosphere corona

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Comparison between the eruptive X2.2 flare on 2011 February15 and confined X3.1 flare on 2014 October 24

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Research in Astronomy and Astrophysics 2015年第9期15卷 1537-1546页

作者： Ju Jing Yan Xu Jeongwoo Lee Nariaki V.Nitta Chang Liu Sung-Hong Park thomas wiegelmann Haimin Wang Center for Solar-Terrestrial Research New Jersey Institute of Technology Big Bear Solar Observatory Astronomy Program Department of Physics and Astronomy Seoul National University Lockheed Martin Solar and Astrophysics Laboratory Institute for Astronomy Astrophysics Space Applications and Remote Sensing (IAASARS)National Observatory of Athens Max-Planck-Institut fuer Sonnensystemforschung

We compare two contrasting X-class flares in terms of magnetic free energy, relative magnetic helicity and decay index of the active regions （ARs） in which they occurred. The events in question are the eruptive X2.2 flare from AR 11158 accompanied by a halo coronal mass ejection （CME） and the confined X3.1 flare from AR 12192 with no associated CME. These two flares exhibit similar behavior of free magnetic energy and helicity buildup for a few days preceding them. A major difference between the two flares is found to lie in the time-dependent change of magnetic helicity of the ARs that hosted them. AR 11158 shows a significant decrease in magnetic helicity starting -4 hours prior to the flare, but no apparent decrease in helicity is observed in AR 12192. By examining the magnetic helicity injection rates in terms of sign, we confirmed that the drastic decrease in magnetic helicity before the eruptive X2.2 flare was not caused by the injection of reversed helicity through the photosphere but rather the CME-related change in the coronal magnetic field. Another major difference we find is that AR 11158 had a significantly larger decay index and therefore weaker overlying field than AR 12192. These results suggest that the coronal magnetic helicity and the decay index of the overlying field can provide a clue about the occurrence of CMEs.

关键词： Sun： magnetic topology -- Sun： evolution -- Sun： flares -- Sun： coronal mass ejections （CMEs）

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