Spacecraft charging and ion wake formation in the near-Sun environment
Spacecraft charging and ion wake formation in the near-Sun environment
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DOI：
10.1063/1.3457484
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发表时间：
2010-07-01
影响因子：
2.2
通讯作者：
Wygant, J. R.
中科院分区：
文献类型：
--
作者：
Ergun, R. E.;Malaspina, D. M.;Wygant, J. R.
采用三维自洽程序求解了航天器周围的静电势结构。数值解表明，在一定条件下，尽管有很强的光电子流，航天器仍能产生负电势。负电位是由于航天器表面附近的静电屏障，可以将大部分光电子通量反射回航天器。如果（1）航天器表面的光电子密度大大超过环境等离子体密度，（2）航天器的尺寸明显大于光电子的局部德拜长度，（3）热电子能量远远大于逃逸光电子的特征能量，就会形成静电势垒。所有这些条件都存在于太阳附近。数值解还表明，航天器的负电位可以被离子尾流放大。离子尾流的负电势防止二次电子从与尾流接触的航天器部分逃逸。这些发现可能对未来更接近太阳的航天器任务很重要，例如太阳轨道器和太阳探测器Plus。(C)2010年美国物理学会。[doi：10.1063/1.3457484]
A three-dimensional, self-consistent code is employed to solve for the static potential structure surrounding a spacecraft in a high photoelectron environment. The numerical solutions show that, under certain conditions, a spacecraft can take on a negative potential in spite of strong photoelectron currents. The negative potential is due to an electrostatic barrier near the surface of the spacecraft that can reflect a large fraction of the photoelectron flux back to the spacecraft. This electrostatic barrier forms if (1) the photoelectron density at the surface of the spacecraft greatly exceeds the ambient plasma density, (2) the spacecraft size is significantly larger than local Debye length of the photoelectrons, and (3) the thermal electron energy is much larger than the characteristic energy of the escaping photoelectrons. All of these conditions are present near the Sun. The numerical solutions also show that the spacecraft's negative potential can be amplified by an ion wake. The negative potential of the ion wake prevents secondary electrons from escaping the part of spacecraft in contact with the wake. These findings may be important for future spacecraft missions that go nearer to the Sun, such as Solar Orbiter and Solar Probe Plus. (C) 2010 American Institute of Physics. [doi:10.1063/1.3457484]