Magnetohydrodynamic Simulation of Magnetic Null-point Reconnections and Coronal Dimmings during the X2.1 Flare in NOAA AR 11283
Magnetohydrodynamic Simulation of Magnetic Null-point Reconnections and Coronal Dimmings during the X2.1 Flare in NOAA AR 11283
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DOI：
10.3847/1538-4357/abb8d2
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发表时间：
2020-09
期刊：
影响因子：
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通讯作者：
A. Prasad;K. Dissauer;Q. Hu;R. Bhattacharyya;A. Veronig;Sanjay Kumar;B. Joshi
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文献类型：
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作者：
A. Prasad;K. Dissauer;Q. Hu;R. Bhattacharyya;A. Veronig;Sanjay Kumar;B. Joshi
利用光球矢量磁图外推的初始非无力磁场，模拟了活动区域NOAA 11283的磁流体动力学。我们重点研究了2011年9月6日22:21 UT （SOL2011-09-06T22:21X2.1）的X2.1耀斑磁零点的磁重联，随后出现了圆形耀斑带和日冕变暗。从外推的初始磁场显示一个三维（3D）零拓扑覆盖剪切拱廊。在耀斑之前，磁环由于初始洛伦兹力而上升，并在三维零点处重新连接，导致受限等离子体的膨胀和损失，从而产生观测到的耀斑前日冕变暗。此外，模拟动力学记录了通过重新连接将扭曲从拱廊传递到覆盖的环路，形成一种通量绳。由绳索和低洼拱廊组成的非平行场线形成x型几何形状。重要的是，在三维零和x型几何上的同时重连可以解释观察到的圆形和平行耀斑带。在3D零点处的重连将封闭的内部脊柱场线转换为外部脊柱的开放场线。这些开放磁场线的脚点对应于一个环形的日冕变暗区域，沿着圆顶。此外，磁通绳由于这些重连而分叉，这也导致了开放磁力线的产生。等离子体沿开放磁场线的损失可以潜在地解释观测到的日冕变暗。
The magnetohydrodynamics of active region NOAA 11283 is simulated using an initial non-force-free magnetic field extrapolated from its photospheric vector magnetogram. We focus on the magnetic reconnections at a magnetic null point that participated in the X2.1 flare on 2011 September 6 around 22:21 UT (SOL2011-09-06T22:21X2.1) followed by the appearance of circular flare ribbons and coronal dimmings. The initial magnetic field from extrapolation displays a three-dimensional (3D) null topology overlying a sheared arcade. Prior to the flare, magnetic loops rise due to the initial Lorentz force, and reconnect at the 3D null, leading to expansion and loss of confined plasma that produce the observed pre-flare coronal dimmings. Further, the simulated dynamics documents the transfer of twist from the arcade to the overlying loops through reconnections, developing a flux rope. The nonparallel field lines comprising the rope and lower-lying arcades form an X-type geometry. Importantly, the simultaneous reconnections at the 3D null and the X-type geometry can explain the observed circular and parallel flare ribbons. Reconnections at the 3D null transform closed inner spine field lines into open field lines of the outer spine. The footpoints of these open field lines correspond to a ring-shaped coronal dimming region, tracing the dome. Further, the flux rope bifurcates because of these reconnections, which also results in the generation of open magnetic field lines. The plasma loss along the open field lines can potentially explain the observed coronal dimming.