The origin of underdense plasma downflows associated with magnetic reconnection in solar flares
The origin of underdense plasma downflows associated with magnetic reconnection in solar flares
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DOI：
10.1038/s41550-021-01570-2
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发表时间：
2021-11
期刊：
影响因子：
14.1
通讯作者：
Chengcai Shen;Bin Chen;K. Reeves;Sijie Yu;V. Polito;Xiao-yang Xie
中科院分区：
文献类型：
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作者：
Chengcai Shen;Bin Chen;K. Reeves;Sijie Yu;V. Polito;Xiao-yang Xie
磁重联是一个普遍的过程，它为太阳耀斑、地磁亚暴和一些天体物理喷流等爆炸性能量释放事件提供动力。磁重联的一个特征是产生接近等离子体速度的快速重联流出射流。在爆发的太阳耀斑中，黑色的指状等离子体向耀斑拱廊方向向下流动，通常被认为是这种重联驱动的外流的主要观测证据。然而，它们的速度往往比重联理论中预期的要慢得多，这对标准耀斑模型中重联驱动的能量释放情景提出了挑战。本文提出了太阳耀斑的三维磁流体动力学模型。通过将模型预测与观测到的等离子体下流特征进行比较，我们得出结论，这些暗下流是自组织结构，形成于耀斑终止激波下方的湍流界面区域，在该区域，流出物与耀斑拱门相遇，这种现象类似于超新星遗迹中类似结构的形成。这个界面区域承载着无数的湍流、电子电流和冲击，对耀斑能量释放和粒子加速至关重要。
Magnetic reconnection is a universal process that powers explosive energy-release events such as solar flares, geomagnetic substorms and some astrophysical jets. A characteristic feature of magnetic reconnection is the production of fast reconnection outflow jets near the plasma Alfvén speeds,. In eruptive solar flares, dark finger-shaped plasma downflows moving toward the flare arcade have been commonly regarded as the principal observational evidence for such reconnection-driven outflows,. However, they often show a speed much slower than that expected in reconnection theories,, challenging the reconnection-driven energy-release scenario in standard flare models. Here we present a three-dimensional magnetohydrodynamics model of solar flares. By comparing the model predictions with the observed plasma downflow features, we conclude that these dark downflows are self-organized structures formed in a turbulent interface region below the flare termination shock where the outflows meet the flare arcade, a phenomenon analogous to the formation of similar structures in supernova remnants. This interface region hosts a myriad of turbulent flows, electron currents and shocks, crucial for flare energy release and particle acceleration.