低轨道磁化等离子体中运动航天器等离子体鞘层特性

PLASMA SHEATH OF MOVING SPACECRAFT IN MAGNETIZED PLASMA OF LOW EARTH ORBIT

用二维静电粒子模拟程序研究了在低轨道磁化等离子体中航天器充电过程和等离子体鞘层结构．采用磁化等离子体流经航天器的物理模型，并且考虑零级对流电场的影响．结果表明航天器在低轨道空间飞行时，如果不考虑光电子流，航天器会在短时间内（ｔ＝５４ω_（ｐｅ）^（－１），ω_（ｐｅ）是电子等离子体频率）快速充电到平衡电位。在不考虑航天器运动的情况下其周围等离子体鞘层结构是围绕航天器对称的，等离子体鞘层宽度约２．４个德拜（Ｄｅｂｙｅ）长度．当考虑航天器运动时，航天器的平衡负电位绝对值减小．且在背离航天器运动方向上等离子体鞘层宽度为８．３个德拜长度．磁场的增大使负的平衡电位绝对值变小，当航天器运动从平行于磁场方向转向垂直于磁场方向时，航天器负平衡电位的绝对值减小．

The charging process and plasma sheath structure of moving spacecraft in magnetized plasma of low earth orbit (LEO) are studied by means of 2.5-D electrostatic code. The relative motion is simulated by a plasma flowing past the probe and therefore a convection electric field is imposed. The results show that in the LEO, the spacecraft is quickly (during a time interval t = 54ω_(pe)^(-1) .ω_(pe) is electron cyclotron frequency) charged up to the equilibrium negative potential. The increase of magnetic field makes absolute value of the negative potential decrease. The plasma sheath is symmetric around the spacecraft if the motion of the plasma is not considered, and is about several Debye length. The motion of the plasma will make the plasma sheath extend in the wake region.