Collisional damping rates for plasma waves

TL;DR

This paper numerically evaluates rigorous collisional damping rates for plasma waves, revealing they are significantly lower than traditional estimates, which impacts understanding of wave attenuation in various plasma environments.

Contribution

It provides the first numerical assessment of rigorous collisional damping rates for plasma waves using a Maxwellian distribution, contrasting with heuristic formulas.

Findings

Rigorous damping rates are much lower than Spitzer estimates.

Traditional approaches overestimate wave attenuation due to collisions.

Results have implications for plasma physics in laboratory, space, and astrophysical contexts.

Abstract

The distinction between the plasma dynamics dominated by collisional transport versus collective processes has never been rigorously addressed until recently. A recent paper [Yoon et al., Phys. Rev. E 93, 033203 (2016)] formulates for the first time, a unified kinetic theory in which collective processes and collisional dynamics are systematically incorporated from first principles. One of the outcomes of such a formalism is the rigorous derivation of collisional damping rates for Langmuir and ion-acoustic waves, which can be contrasted to the heuristic customary approach. However, the results are given only in formal mathematical expressions. The present Brief Communication numerically evaluates the rigorous collisional damping rates by considering the case of plasma particles with Maxwellian velocity distribution function so as to assess the consequence of the rigorous formalism in a quantitative manner. Comparison with the heuristic ("Spitzer") formula shows that the accurate damping rates are much lower in magnitude than the conventional expression, which implies that the traditional approach over-estimates the importance of attenuation of plasma waves by collisional relaxation process. Such a finding may have a wide applicability ranging from laboratory to space and astrophysical plasmas.