# Temperature Anisotropy Relaxation of the One-Component Plasma

## TL;DR

This study evaluates the relaxation rate of temperature anisotropy in a one-component plasma using molecular dynamics simulations, comparing results with various kinetic theories across different coupling regimes.

## Contribution

It provides a comprehensive comparison of kinetic theories with simulations for anisotropy relaxation, including strong coupling effects often neglected by traditional models.

## Key findings

- Dynamic screening has negligible effect on relaxation rate.
- Oscillations and delayed relaxation occur at strong coupling, not captured by existing theories.
- Simulation results align with weakly coupled theories but reveal limitations at strong coupling.

## Abstract

The relaxation rate of a Maxwellian velocity distribution function that has an initially anisotropic temperature $(T_\parallel \neq T_\perp)$ is an important physical process in space and laboratory plasmas. It is also a canonical example of an energy transport process that can be used to test theory. Here, this rate is evaluated using molecular dynamics simulations of the one-component plasma. Results are compared with the predictions of four kinetic theories; two treating the weakly coupled regime (1) the Landau equation, and (2) the Lenard-Balescu equation, and two that attempt to extend the theory into the strongly coupled regime (3) the effective potential theory and (4) the generalized Lenard-Balescu theory. The role of dynamic screening is studied, and is found to have a negligible influence on this transport rate. Oscillations and a delayed relaxation onset in the temperature profiles are observed at strong coupling, which are not described by the kinetic theories.