Collisionless relaxation of ion distributions downstream of laminar quasi-perpendicular shocks
Collisionless relaxation of ion distributions downstream of laminar quasi-perpendicular shocks
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DOI：
10.1029/2009ja014365
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发表时间：
2009-09
影响因子：
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通讯作者：
L. Ofman;M. Balikhin;C. Russell;M. Gedalin
中科院分区：
文献类型：
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作者：
L. Ofman;M. Balikhin;C. Russell;M. Gedalin
[1]入射离子的定向流动提供了自由能，该自由能在加热的离子和电子、加速的粒子和磁压缩之间的冲击中重新分布。在低马赫数的层流激波中，转换的主要通道是下游的回旋离子。就在激波过渡之后，离子分布基本上是非各向异性的，这导致离子压力的空间周期性变化，并且因此导致磁场的时间稳定的下游振荡。在不存在显著水平的非平稳性的情况下，陀螺化是由于陀螺相位混合和缓慢。理论分析的现象和支持混合模拟。结果表明，这些振荡在低马赫数低β激波时更容易观察到，而在高马赫数或高β激波时，它们可能被穿过激波的波所掩盖。
[1] Directed flow of incident ions provides the free energy which is redistributed in a shock among heated ions and electrons, accelerated particles, and magnetic compression. In low Mach number laminar shock the main channel of conversion is into downstream gyrating ions. Just behind the shock transition the ion distribution is substantially nongyrotropic, which results in spatially periodic variations of the ion pressure and, consequently, in time stationary downstream oscillations of the magnetic field. In the absence of significant level of nonstationarity, gyrotropization is due to the gyrophase mixing and slow. Theoretical analysis of the phenomenon and supporting hybrid simulations are presented. It is shown that these oscillations are more likely to be observed at low Mach number low β shocks, while at higher Mach numbers or higher β they may be obscured by waves crossing the shocks.