Measurement of magnetic field and relativistic electrons along a solar flare current sheet
Measurement of magnetic field and relativistic electrons along a solar flare current sheet
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沿着太阳耀斑电流片测量磁场和相对论电子
DOI：
10.1038/s41550-020-1147-7
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发表时间：
2020-07-27
期刊：
影响因子：
14.1
通讯作者：
Kong, Xiangliang
中科院分区：
文献类型：
--
作者：
Chen, Bin;Shen, Chengcai;Kong, Xiangliang
在太阳耀斑的标准模型中，假定一个大尺度重联电流片是耀斑能量释放（1-3）和加速粒子（4-6）的中心引擎。然而，由于缺乏对电流片磁性的测量，能量释放和粒子加速在哪里以及如何发生仍然不清楚。在这里，我们报告了测量空间分辨磁场和耀斑加速相对论电子沿电流片特征在太阳耀斑。测量的磁场剖面显示，在极性相反的重联磁力线彼此紧密接近的地方，有一个局部最大值，称为重联X点。测量还揭示了耀斑环顶上方电流片底部附近的局部最小值，称为“磁瓶”。这种空间结构与理论预测（1,7）和数值模拟结果一致。推断在X点附近存在约4000 V m（-1）的强重联电场。然而，这个位置显示出发射微波的相对论性电子的局部耗尽。相反，这些电子集中在磁瓶结构或其附近，其中99%以上的电子每时每刻都停留在那里。我们的观察表明，环顶磁瓶可能是加速和限制相对论性电子的主要场所。对2017年9月10日发生的X8.2太阳耀斑的观测，可以在空间上解析高能电子沿重联电流片的分布。其中99%以上集中在电流片的底部，而不是在重连X点。
In the standard model of solar flares, a large-scale reconnection current sheet is postulated to be the central engine for powering the flare energy release(1-3)and accelerating particles(4-6). However, where and how the energy release and particle acceleration occur remain unclear owing to the lack of measurements of the magnetic properties of the current sheet. Here we report the measurement of the spatially resolved magnetic field and flare-accelerated relativistic electrons along a current-sheet feature in a solar flare. The measured magnetic field profile shows a local maximum where the reconnecting field lines of opposite polarities closely approach each other, known as the reconnection X point. The measurements also reveal a local minimum near the bottom of the current sheet above the flare loop-top, referred to as a 'magnetic bottle'. This spatial structure agrees with theoretical predictions(1,7)and numerical modelling results. A strong reconnection electric field of about 4,000 V m(-1)is inferred near the X point. This location, however, shows a local depletion of microwave-emitting relativistic electrons. These electrons instead concentrate at or near the magnetic bottle structure, where more than 99% of them reside at each instant. Our observations suggest that the loop-top magnetic bottle is probably the primary site for accelerating and confining the relativistic electrons.Observations of the X8.2 solar flare, which happened on 2017 September 10, could spatially resolve the distribution of the energetic electrons along the reconnection current sheet. More than 99% of them are concentrated at the bottom of the current sheet, not at the reconnection X point.