Chirality and magnetic configuration associated with two-ribbon solar flares: AR 10930 versus AR 11158. (arXiv:1810.13124v4 [astro-ph.SR] UPDATED)
<a href="http://arxiv.org/find/astro-ph/1/au:+He_H/0/1/0/all/0/1">Han He</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Wang_H/0/1/0/all/0/1">Huaning Wang</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Yan_Y/0/1/0/all/0/1">Yihua Yan</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Li_B/0/1/0/all/0/1">Bo Li</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Chen_P/0/1/0/all/0/1">P. F. Chen</a>
The structural property of the magnetic field in flare-bearing solar active
regions (ARs) is one of the key aspects for understanding and forecasting solar
flares. In this paper, we make a comparative analysis on the chirality and
magnetic configurations associated with two X-class two-ribbon flares happening
in AR 10930 and AR 11158. The photospheric magnetic fields of the two ARs were
observed by space-based instruments, and the corresponding coronal magnetic
fields were calculated based on the nonlinear force-free field model. The
analysis shows that the electric current in the two ARs was distributed mostly
around the main polarity inversion lines (PILs) where the flares happened, and
the magnetic chirality (indicated by the signs of force-free factor $alpha$)
along the main PILs is opposite for the two ARs, i.e., left-handed ($alpha<0$)
for AR 10930 and right-handed ($alpha>0$) for AR 11158. It is found that, for
both the flare events, a prominent magnetic connectivity (featured by
co-localized strong $alpha$ and strong current density distributions) was
formed along the main PIL before flare and was totally broken after flare
eruption. The two branches of the broken magnetic connectivity, combined with
the prominent magnetic connectivity before flare, compose the opposite magnetic
configurations in the two ARs owing to their opposite chirality, i.e., Z-shaped
configuration in AR 10930 with left-handed chirality and inverse Z-shaped
configuration in AR 11158 with right-handed chirality. It is speculated that
two-ribbon flares can be generally classified to these two magnetic
configurations by chirality in the flare source regions of ARs.
The structural property of the magnetic field in flare-bearing solar active
regions (ARs) is one of the key aspects for understanding and forecasting solar
flares. In this paper, we make a comparative analysis on the chirality and
magnetic configurations associated with two X-class two-ribbon flares happening
in AR 10930 and AR 11158. The photospheric magnetic fields of the two ARs were
observed by space-based instruments, and the corresponding coronal magnetic
fields were calculated based on the nonlinear force-free field model. The
analysis shows that the electric current in the two ARs was distributed mostly
around the main polarity inversion lines (PILs) where the flares happened, and
the magnetic chirality (indicated by the signs of force-free factor $alpha$)
along the main PILs is opposite for the two ARs, i.e., left-handed ($alpha<0$)
for AR 10930 and right-handed ($alpha>0$) for AR 11158. It is found that, for
both the flare events, a prominent magnetic connectivity (featured by
co-localized strong $alpha$ and strong current density distributions) was
formed along the main PIL before flare and was totally broken after flare
eruption. The two branches of the broken magnetic connectivity, combined with
the prominent magnetic connectivity before flare, compose the opposite magnetic
configurations in the two ARs owing to their opposite chirality, i.e., Z-shaped
configuration in AR 10930 with left-handed chirality and inverse Z-shaped
configuration in AR 11158 with right-handed chirality. It is speculated that
two-ribbon flares can be generally classified to these two magnetic
configurations by chirality in the flare source regions of ARs.
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