Changes of magnetic structure in three dimensions associated with the X3.4 flare of 2006 December 13
Changes of magnetic structure in three dimensions associated with the X3.4 flare of 2006 December 13
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DOI：
10.1086/587058
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发表时间：
2008-03-20
影响因子：
7.9
通讯作者：
Wang, Haimin
中科院分区：
文献类型：
--
作者：
Jing, Ju;Wiegelmann, Thomas;Wang, Haimin
最近的观测表明，在耀斑发生后，太阳黑子的结构可以迅速发生不可逆转的变化。最令人费解的结果之一是耀斑后耀斑磁极反转线周围的磁切变增加。然而，所有这些观测都是在光球层进行的。本文研究了2006年12月13日4B/X3.4耀斑相关磁场非位势的高度变化。用Hinode观测到的质量前所未有的矢量磁图作为边界条件，外推了三维非线性无力磁场和位场。前者用最优化算法计算，后者用格林函数法计算。在光球边界，耀斑发生后，在耀斑磁极反转线附近的局部区域，磁切变增大。在海拔逐渐升高的这个地区，计算了两个衡量磁非位势的指标--加权平均切变θ(W)和总磁切变theta B-w。通过比较耀斑前后的高度变化廓线，发现耀斑发生在8 mm以下时，局地的非位势增大，而从该高度开始减小到70 mm左右。超过70毫米时，磁场两次都接近电势。
Recent observations demonstrated that sunspot structure can change rapidly and irreversibly after flares. One of the most puzzling results is the increase in magnetic shear around the flaring magnetic polarity inversion line after flares. However, all these observations were made at the photosphere level. In this Letter, we study the altitude variation of the nonpotentiality of the magnetic fields associated with the 4B/X3.4 flare of 2006 December 13. The vector magnetograms with unprecedented quality from Hinode before and after the flare are used as the boundary conditions to extrapolate the three-dimensional nonlinear force-free magnetic fields and the potential fields. The former are computed with the optimization algorithm and the latter with the Green's function method. At the photosphere boundary, magnetic shear increases after the flare in a local area close to the flaring magnetic polarity inversion line. Two measures of the magnetic nonpotentiality, the weighted mean shear theta(w) and the total magnetic shear theta B-w, are calculated in this area at progressively higher altitude. By comparing their altitude variation profiles before and after the flare, we find that the nonpotentiality of the local area increases after the flare below similar to 8 Mm and decreases from that height to similar to 70 Mm. Beyond 70 Mm, the magnetic fields approach potential for both times.