Effect of gas discharge and magnetic field on plasma layer at the surface in gas flow

Abstract

Summary form only given. When returning to the Earth, the spacecrafts enter the upper atmospheric layers with a hypersonic speed. In this case, the shock heated air around them becomes weakly ionized. The gas ionization behind the shock front is associative in nature and occurs through chemical reactions between fragments of molecules. The formation of a plasma layer near the surfaces of spacecraft causes serious problems related to the blocking of communication channels with the Earth and other spacecraft. A promising way of restoring the radio communications is the application of electrical and magnetic fields for controlling the plasma layer parameters. Sheaths with an almost zero electron density and a high ion density are known to be formed near a surface when an ac or dc gas discharge is ignited in a plasma. Since the electromagnetic waves interact mainly with the plasma electron component, a decrease in electron density ensures the passage of the electromagnetic waves through the plasma sheath. In this work, we consider the combined action of a direct current (DC) discharge and a magnetic field on the plasma flow near a flat surface at a low gas pressure. Our simulations ar e performed using a two dimensional Particle in cell method (PIC MCC). The kinetics of electrons in nitrogen includes elastic collisions, the excitation of rotational, vibrational, and meta stable levels, and ionization. Based on two dimensional kinetic PIC MCC simulations, we considered the possibility of locally controlling the plasma sheath parameters near a flat surface i n a hypersonic flow. We showed that the combined action of D C discharge, a constant voltage, and a magnetic field on the plasma sheath allows the local electron density to be reduced manyfold. We did not consider the effect of gas flow acceleration during the momentum transfer from ions to gas molecules under resonant charge exchange. The gas flow velocity distribution is specified by a model function.