Vlasov simulations of electric propulsion beam

Abstract A grid-based Vlasov simulation model is developed to simulate the two-dimensional unmagnetized electric propulsion (EP) plasma beam emission process. Comparing to the standard fully kinetic Particle-in-Cell simulation, the grid-based Vlasov simulation method eliminates the interference of particle noise and is capable of resolving higher-order velocity moment, such as electron heat flux, accurately. Vlasov simulations are carried out to investigate the effects of microscopic electron kinetics on macroscopic electron thermodynamics in EP beam. We find that the electron velocity distribution function (eVDF) exhibits a near-Maxwellian shape but with a depleted negative velocity tail in the beam direction and a ‘top-hat’ shape in the transverse direction. Macroscopically, the electrons confined within the quasi-neutral beam core region has a near constant temperature along the beam direction but follow a near-adiabatic cooling process as they expand outward in the transverse direction. The electron heat flux is dominated by the x -direction tensor component. The connection between the eVDF skewness and the electron heat flux suggests a pathway to develop a microscopic physics based electron closure relation for macroscopic electron thermodynamic process in unmagnetized plasma beam expansion.