高马赫数准垂直激波中电子加热的马赫数依赖性
Mach Number Dependence of Electron Heating in High Mach Number Quasiperpendicular Shocks
摘要：
利用PIC（Particle-In-Cell）模拟和模型分析，研究了大范围马赫数准垂直激波转捩区微不稳定性对电子加热的影响。在模型分析中，作为微观不稳定性结果的有效电子温度饱和水平是从相对低（高）马赫数激波的扩展准线性（捕获）分析中估计的。在低马赫数区，MTSI（修正双流不稳定性）占主导地位;在高马赫数区，BI（布尼曼不稳定性）占主导地位。结果表明，MTSI主导情况下有效电子温度与马赫数的依赖关系与BI主导情况有本质不同。通过MTSI的有效电子温度对马赫数的依赖性不大，虽然通过BI的有效电子温度与过去的研究一样随马赫数而增加。结果证实，在定性和定量水平上与PIC模拟一致。模型分析预测，在马赫数为几十时，可能出现一个临界马赫数，超过这个临界马赫数，电子加热率急剧上升。
英文摘要：
Efficiency of electron heating through microinstabilities generated in the transition region of a quasi-perpendicular shock for wide ange of Mach numbers is investigated by utilizing PIC (Particle-In-Cell) simulation and model analyses. In the model analyses saturation levels of effective electron temperature as a result of microinstabilities are estimated from an extended quasilinear (trapping) analysis for relatively low (high) Mach number shocks. Here, MTSI (modified two-stream instability) is assumed to become dominant in low Mach number regime, while BI (Buneman instability) to become dominant in high Mach number regime, respectively. It is revealed that Mach number dependence of the effective electron temperature in the MTSI dominant case is essentially different from that in the BI dominant case. The effective electron temperature through the MTSI does not depend much on the Mach number, although that through the BI increases with the Mach number as in the past studies. The results are confirmed to be consistent with the PIC simulations both in qualitative and quantitative levels. The model analyses predict that a critical Mach number above which steep rise of electron heating rate occurs may arise at the Mach number of a few tens.
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