Fully kinetic simulations of strong steady-state collisional planar plasma shocks

TL;DR

This paper presents the first steady-state fully kinetic simulations of strong plasma shocks, revealing nonlocal electron heat transport effects and a collapse in the precursor electric field, with implications for shock modeling.

Contribution

It introduces the first steady-state kinetic simulations of strong plasma shocks, confirming results with two codes and analyzing nonlocal electron heat transport effects.

Findings

Kinetic electrons do not alter shock structure significantly.

Nonlocal electron heat transport causes preheat layer rearrangement.

Precursor electric field collapses at the preheat layer edge.

Abstract

We report on the first steady-state simulations of strong plasma shocks with fully kinetic ions and electrons, independently confirmed by two fully kinetic codes (an Eulerian continuum and a Lagrangian particle-in-cell). While kinetic electrons do not fundamentally change the shock structure as compared with fluid electrons, we find an appreciable rearrangement of the preheat layer, associated with nonlocal electron heat transport effects. The electron heat flux profile qualitatively agrees between kinetic and fluid electron models, suggesting a certain level of "stiffness", though substantial nonlocality is observed in the kinetic heat flux. We also find good agreement with nonlocal electron heat-flux closures proposed in the literature. Finally, in contrast to the classical hydrodynamic picture, we find a significant collapse in the "precursor" electric-field shock at the preheat layer edge, which correlates with the electron-temperature gradient relaxation.