Plasma wake simulations and object charging in a shadowed lunar crater during a solar storm
Plasma wake simulations and object charging in a shadowed lunar crater during a solar storm
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太阳风暴期间阴影月球陨石坑中的等离子体尾流模拟和物体充电
DOI：
10.1029/2012je004094
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发表时间：
2012
影响因子：
--
通讯作者：
T. Stubbs
中科院分区：
文献类型：
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作者：
M. Zimmerman;T. Jackson;W. Farrell;T. Stubbs
[1]在永久阴影的月球陨石坑内，太阳风的水平流动受到上游地形的阻碍，形成了等离子体尾流，通过静电将离子转移到陨石坑底部，并产生可以达到千伏的表面电位。在本工作中，我们使用动力学等离子体模拟来研究太阳风暴期间月球环形山尾迹的形态。计算结果以离子马赫数、凹坑深度与等离子体德拜长度之比、峰值二次电子产额以及峰值二次产额时电子温度与电子碰撞能之比等前导无量纲比来表示。这一小部分比率允许将其推广到更广泛的情况。动力学仿真结果被前馈到巡回航天员的等效电路模型中。在等离子体电流非常低的环境中，宇航服的摩擦电荷实际上是永久的，这是在阴暗的月球区域漫游的一个关键的工程问题。最后，用模拟的离子通量研究了理想弹坑内的溅射和注入过程。这表明，在永久阴影地形附近形成的等离子体小尾迹物理可能在调节月球两极挥发分神秘的空间分布方面起到关键作用。
[1] Within a permanently shadowed lunar crater the horizontal flow of solar wind is obstructed by upstream topography, forming a plasma wake that electrostatically diverts ions toward the crater floor and generates a surface potential that can reach kilovolts. In the present work kinetic plasma simulations are employed to investigate the morphology of a lunar crater wake during passage of a solar storm. Results are cast in terms of leading dimensionless ratios including the ion Mach number, ratio of crater depth to plasma Debye length, peak secondary electron yield, and electron temperature versus electron impact energy at peak secondary yield. This small set of ratios allows generalization to a much wider range of scenarios. The kinetic simulation results are fed forward into an equivalent-circuit model of a roving astronaut. In very low-plasma-current environments triboelectric charging of the astronaut suit becomes effectively perpetual, representing a critical engineering concern for roving within shadowed lunar regions. Finally, simulated ion fluxes are used to explore sputtering and implantation processes within an idealized crater. It is suggested that the physics of plasma miniwakes formed in the vicinity of permanently shadowed topography may play a critical role in modulating the enigmatic spatial distribution of volatiles at the lunar poles.