Ionization Around a High-Voltage Body in Magnetized Nonflowing Ionospheric Plasma

摘要

The electron sheath structure around a cylindrical body with a finite length that is biased to a high positive potential in a magnetized nonflowing ionospheric plasma with enhanced neutral density is studied. The results of Monte-Carlo particle-in-cell simulations show that the sheath boundary increases as the neutral density increases and ionization occurs inside the sheath. There is a critical neutral density above which the sheath expands infinitely, i.e., sheath explosion. A formula of the critical neutral density is derived through theoretical formulation. The theoretical results are compared with the results of the simulation, which serves as a numerical experiment, to check the validity of various assumptions made to derive a simple formula for the critical neutral density. The theoretical formula predicts that the critical neutral density lies in a narrow range of 6 x 10~(16) ～ 6 x 10~(17) m~(-3), leaving little dependence on the spacecraft surface potential at typical ionospheric conditions.