A Data-constrained Magnetohydrodynamic Simulation of the X1.0 Solar Flare of 2021 October 28

The solar active region NOAA 12887 produced a strong X1.0 flare on 2021 October 28, which exhibits X-shaped flare ribbons and a circle-shaped erupting filament. To understand the eruption process with these characteristics, we conducted a data-constrained magnetohydrodynamics simulation using a nonlinear force-free field of the active region about an hour before the flare as the initial condition. Our simulation reproduces the filament eruption observed in the Hα images of GONG and the 304 Å images of SDO/AIA, and suggests that two mechanisms can possibly contribute to the magnetic eruption. One is the torus instability of the preexisting magnetic flux rope (MFR) and the other is upward pushing by magnetic loops newly formed below the MFR via continuous magnetic reconnection between two sheared magnetic arcades. The presence of this reconnection is evidenced by the SDO/AIA observations of the 1600 Å brightening in the footpoints of the sheared arcades at the flare onset. To clarify which process is more essential for the eruption, we performed an experimental simulation in which the reconnection between the sheared field lines is suppressed. In this case too, the MFR could erupt, but at a much reduced rising speed. We interpret this result as indicating that the eruption is not only driven by the torus instability, but additionally accelerated by newly formed and rising magnetic loops under continuous reconnection.

太阳活动区NOAA 12887在2021年10月28日产生了一次强烈的X1.0级耀斑，该耀斑呈现出X形耀斑带和一个圆形爆发的暗条。为了理解具有这些特征的爆发过程，我们以耀斑发生前约一小时活动区的非线性无力场作为初始条件，进行了一次数据约束的磁流体动力学模拟。我们的模拟重现了在GONG的Hα图像和SDO/AIA的304 Å图像中观测到的暗条爆发，并表明两种机制可能对磁爆发有贡献。一种是预先存在的磁通量绳（MFR）的环面不稳定性，另一种是通过两个剪切磁拱之间的持续磁重联在MFR下方新形成的磁环向上的推动。在耀斑爆发时SDO/AIA观测到剪切拱足点处1600 Å增亮，证明了这种重联的存在。为了阐明哪个过程对爆发更为关键，我们进行了一次实验模拟，其中抑制了剪切场线之间的重联。在这种情况下，MFR也能够爆发，但上升速度大幅降低。我们将这一结果解释为表明爆发不仅由环面不稳定性驱动，而且在持续重联下由新形成并上升的磁环进一步加速。