Kinetic instability of ion acoustic mode in permeating plasmas

TL;DR

This paper investigates the kinetic instability of ion acoustic waves in permeating plasmas, revealing that relative plasma motion can induce instabilities at velocities below the ion acoustic speed, relevant for space and astrophysical environments.

Contribution

It introduces a new understanding of ion acoustic instability thresholds in permeating plasmas, extending previous models to include static and flowing plasma interactions.

Findings

Instability threshold can be below the ion acoustic speed in permeating plasmas.

Current-less instability can occur in space and astrophysical plasmas.

Theoretical analysis of plasma interactions reveals new instability conditions.

Abstract

In plasmas with electron drift (current) relative to static ions, the ion acoustic wave is subject to the kinetic instability which takes place if the directed electron speed exceeds the ion acoustic speed. The instability threshold becomes different in the case of one quasi-neutral electron-ion plasma propagating through another static quasi-neutral (target) plasma. The threshold velocity of the propagating plasma may be well below the ion acoustic speed of the static plasma. Such a current-less instability may frequently be expected in space and astrophysical plasmas.