Computer studies of the dynamic evolution of the geomagnetic tail
Computer studies of the dynamic evolution of the geomagnetic tail
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地磁尾动态演化的计算机研究
DOI：
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发表时间：
1980
期刊：
影响因子：
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通讯作者：
J. Birn
中科院分区：
文献类型：
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作者：
J. Birn
利用二维含时非线性阻性MHD程序，数值研究了伸展磁尾结构的动态演化。在理想磁流体中，初始构型是稳定的。这种不稳定的演化是通过施加有限的电阻率来启动的。
与边界条件完全无关的是，下列现象自发发展：等离子体片变薄，磁场构型的拓扑变化，形成具有几乎静止的X线的中性线，大的感应交叉尾电场，磁场到动能的转换，导致靠近中性片的强烈的向地面和向尾部的流动，以及在中性片之外平行于磁场的流动的重要部分。这种流动使横跨等离子体片边界的符号在X线的尾部反转。结果支持磁层亚暴撕裂理论。在后期，X线周围的位形与稳态重联理论得到的位形相似，特别是我们发现在磁场分隔线的下游形成了两个电流层，这可能代表结构发展成慢激波。
The dynamic evolution of a stretched magnetotail configuration is investigated numerically by means of a two-dimensional time-dependant nonlinear resistive MHD code. The initial configuration is shown to be stable in ideal MHD. The unstable evolution is initiated by imposing a finite resistivity.
Rather independently of the boundary conditions, the following phenomena develop spontaneously: plasma sheet thinning, topological changes of the magnetic field configuration, the formation of neutral lines with an almost stationary X line, large induced cross-tail electric fields, conversion of magnetic to kinetic energy resulting in strong earthward and tailward flow close to the neutral sheet, and outside the neutral sheet a significant part of the flow parallel to the magnetic field. This flow reverses sign across the plasma sheet boundary tailward of the X line. The results support the tearing theory of magnetospheric substorms. At the later stages the configuration around the X line is similar to that obtained from steady state reconnection theory; in particular we found that two current layers form downstream of the magnetic field separatrix, which may represent structures developing into slow shock waves.