Ionospheric plasma flow over large high-voltage space platforms. I: Ion-plasma–time scale interactions of a plate at zero angle of attack

Abstract

Theory and particle simulation results are presented for the ionospheric plasma flow over large, high-voltage space platforms. In this paper, dynamic interactions of a negatively biased plate at a zero angle of attack on the ion-plasma–time scale are emphasized. Results of the transient plasma response to a rapid surface potential change show that ion-acoustic disturbances are generated by the leading edge, and they evolve to form a Mach wedge expansion fan. The transient ion current exhibits a strong overshoot in the first few ion-plasma periods. It is shown that the current overshoot is due to the ions trapped within the initial sheath, and its magnitude is proportional to the plate dimension and the square root of the surface voltage. Simulations of time-dependent interactions of a plate connected to external circuits are also performed. A rapidly changing voltage source may cause a very complex transient current and surface voltage due to the coupling of the transient plasma and circuit properties. Interactions of a plate with electron beam emissions are also studied, and the beam effects on the sheath structure and ion current collection are discussed.