Collisional energy transfer in two-component plasmas

TL;DR

This paper investigates energy transfer and stability in two-component plasmas, showing that collisional effects do not destabilize ion acoustic modes and that potential instabilities are suppressed by rapid relaxation times.

Contribution

It clarifies the role of collisional energy transfer in plasma stability and resolves contradictions in previous research by analyzing relaxation times and instabilities.

Findings

Friction does not affect ion acoustic modes in quasi-neutral plasmas.

Potential instabilities driven by collisional energy transfer are suppressed.

Relaxation times are shorter than growth rates, preventing instabilities.

Abstract

The friction in plasmas consisting of two species with different temperatures is discussed together with the consequent energy transfer. It is shown that the friction between the two species has no effect on the ion acoustic mode in a quasi-neutral plasma. Using the Poisson equation instead of the quasi-neutrality reveals the possibility for an instability driven by the collisional energy transfer. However, the different starting temperatures of the two species imply an evolving equilibrium. It is shown that the relaxation time of the equilibrium electron-ion plasma is, in fact, always shorter than the growth rate time, and the instability can thus never effectively take place. The results obtained here should contribute to the definite clarification of some contradictory results obtained in the past.