A thin-shell instability in collisionless plasma

TL;DR

This paper demonstrates through PIC simulations that a thin-shell instability, similar to the astrophysical phenomenon, can occur in collisionless plasma, leading to growing spatial modulations of the shell structure.

Contribution

It introduces the first simulation-based evidence of thin-shell instability in collisionless plasma, extending the understanding of plasma instabilities beyond collisional regimes.

Findings

The instability causes the shell to develop connected linear patches.

The amplitude of the modulation grows and saturates after about ten inverse proton plasma frequencies.

The process is analogous to the astrophysical thin-shell instability in a collisionless context.

Abstract

The thin-shell instability has been named as one process, which can generate entangled structures in astrophysical plasma on collisional (fluid) scales. It is driven by a spatially varying imbalance between the ram pressure of the inflowing upstream plasma and the downstream's thermal pressure at a non-planar shock. Here we show by means of a particle-in-cell (PIC) simulation that an analogue process can destabilize a thin shell formed by two interpenetrating, unmagnetized and collisionless plasma clouds. The amplitude of the shell's spatial modulation grows and saturates after about ten inverse proton plasma frequencies, when the shell consists of connected piecewise linear patches.