A simulation study on reconnection and small‐scale plasmoid formation
A simulation study on reconnection and small‐scale plasmoid formation
复制标题
重连接和小规模等离子体团形成的模拟研究
DOI：
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发表时间：
1987
期刊：
影响因子：
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通讯作者：
D. Roth
中科院分区：
文献类型：
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作者：
M. Scholer;D. Roth
利用二维含时可压缩电阻MHD程序研究了平面电流片中的磁场重联。与当前板材半厚相比，系统长度较大。允许异常电阻率随电流密度或漂移速度增长。重新连接不是强制的，而是由随后被切断的小的局部电阻启动的。快速重联发展自洽与缓慢的冲击从X点和快速模式扩展上游延伸。一个慢模膨胀风扇在慢模激波的上游引导向X点的等离子体流。在电流依赖电阻率的情况下，重联率再次降低，这导致了分界线的平坦化和长电流层。次级撕裂产生一对新的X点，它们是重连的活性位点。对于低等离子体{β}，两个发育中的等离子体团立即合并成一个。对于高等离子体{β}，重联在所有三个X点进行，导致8字形磁岛结构。在漂移速度依赖电阻率和低等离子体{beta}值的情况下，二次撕裂发生在沿沿着themore>> x轴的低密度位置（大电阻率）。等离子体团合并，新的X点进一步发展。等离子体团的不断发展及其随后的合并导致大规模的等离子体团填充整个计算箱。对于高等离子体{β}值（小的可压缩性），在初始X点的电阻率（和重连率）保持恒定，电流片不伸长，并且没有等离子体团发展，尽管系统长度很大。结果进行了讨论，最近的观测ISEE 3在遥远的尾巴。«少
Magnetic reconnection in a plane current sheet is investigated by means of a two-dimensional time dependent compressible resistive MHD code. The system length is large compared to the current sheet half thickness. The anomalous resistivity is allowed to grow with either the electrical current density or the drift velocity. Reconnection is not forced, but is initiated by a small localized resistivity which is subsequently switched off. Fast reconnection develops self-consistently with slow shocks extending from the X point and a fast mode expansion upstream. A slow mode expansion fan leads upstream of the slow mode shocks to a plasma flow toward the X point. In the case of current dependent resistivity the reconnection rate decreases again, which leads to a flattening of the separatrices and a long current layer. Secondary tearing produces a new pair of X points which are active sites of reconnection. For low plasma {beta} the two developing plasmoids immediately merge into a single one. For high plasma {beta}, reconnection proceeds at all three X points leading to a figure-8 magnetic island structure. In the case of drift velocity dependent resistivity and low plasma {beta} values the secondary tearing occurs at locations of low density along themore » x axis (large resistivity). The plasmoids merge, and new X points develop further out. Continuous development of plasmoids and their subsequent coalescence leads to a large-scale plasmoid filling the whole computational box. For high plasma {beta} values (small compressibility) the resistivity (and the reconnection rate) at the initial X point stays constant, the current sheet does not elongate, and no plasmoid develops, although the system length is large. The results are discussed in relation to recent observations by ISEE 3 in the distant tail.« less