Low Mach-number collisionless electrostatic shocks and associated ion acceleration

TL;DR

This paper investigates low Mach-number collisionless electrostatic shocks using semi-analytical models and kinetic simulations, revealing how impurities and temperature ratios influence shock properties and ion reflection.

Contribution

It introduces a semi-analytical solution for low Mach-number shocks and demonstrates its agreement with kinetic simulations, highlighting impurity effects on shock dynamics.

Findings

Impurities significantly alter shock potential and Mach number.

Heavy ion plasmas reflect most hydrogen impurity ions.

Semi-analytical model accurately reproduces kinetic simulation results.

Abstract

The existence and properties of low Mach-number ($M \gtrsim 1$) electrostatic collisionless shocks are investigated with a semi-analytical solution for the shock structure. We show that the properties of the shock obtained in the semi-analytical model can be well reproduced in fully kinetic Eulerian Vlasov-Poisson simulations, where the shock is generated by the decay of an initial density discontinuity. Using this semi-analytical model, we study the effect of electron-to-ion temperature ratio and presence of impurities on both the maximum shock potential and Mach number. We find that even a small amount of impurities can influence the shock properties significantly, including the reflected light ion fraction, which can change several orders of magnitude. Electrostatic shocks in heavy ion plasmas reflect most of the hydrogen impurity ions.