http://arxiv.org/abs/1810.13124
Magnetic configuration of flare-bearing active regions (ARs) is one key aspect for understanding the initiation mechanism of solar flares. In this paper, we perform a comparative analysis between the magnetic configurations of two X-class two-ribbon flares happened in AR 10930 (on 2006 December 13) and AR 11158 (on 2011 February 15), whose photospheric magnetic fields were observed by Hinode and SDO satellites, respectively, and coronal magnetic fields were calculated based on nonlinear force-free field model. The analysis shows that both the flares initiated in local areas with extremely strong current density intensity, and the magnetic field chirality (indicated by sign of force-free factor {\alpha}) along the main polarity inversion line (PIL) is opposite for the two ARs, that is, left-hand ({\alpha}<0) for AR 10930 and right-hand ({\alpha}>0) for AR 11158. Our previous study (He et al. 2014) showed that, for the flare of AR 10930, a prominent magnetic connectivity was formed above the main PIL before the flare and was totally broken after the flare eruption, and the two branches of broken magnetic connectivity combined with the isolated electric current at the magnetic connectivity breaking site compose a Z-shaped configuration. In this work, we find similar result for the flare of AR 11158 except that its magnetic configuration is inverse Z-shaped, which corresponds to the right-hand chirality of AR 11158 in contrast to the left-hand chirality of AR 10930. We speculate that two-ribbon flares can be generally classified to these two magnetic configurations by chirality ({\alpha} signs) of ARs.
H. He, H. Wang, Y. Yan, et. al.
Thu, 1 Nov 18
28/76
Comments: 12 pages, 7 figures, 2 tables, initial version
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