Pair plasma relaxation time scales

TL;DR

This study numerically calculates the relaxation time scales to thermal equilibrium for optically thick electron-positron plasmas with baryon loading, covering a wide range of energies and compositions relevant to laboratory and astrophysical contexts.

Contribution

It provides detailed relativistic Boltzmann equation solutions for plasma thermalization times across diverse energy densities and baryonic loadings, including limiting cases.

Findings

Thermalization times vary significantly with energy density and baryon loading.

Pure electron-positron and electron-proton plasmas exhibit distinct relaxation behaviors.

Results are applicable to laboratory experiments and astrophysical models involving pair plasmas.

Abstract

By numerically solving the relativistic Boltzmann equations, we compute the time scale for relaxation to thermal equilibrium for an optically thick electron-positron plasma with baryon loading. We focus on the time scales of electromagnetic interactions. The collisional integrals are obtained directly from the corresponding QED matrix elements. Thermalization time scales are computed for a wide range of values of both the total energy density (over 10 orders of magnitude) and of the baryonic loading parameter (over 6 orders of magnitude). This also allows us to study such interesting limiting cases as the almost purely electron-positron plasma or electron-proton plasma as well as intermediate cases. These results appear to be important both for laboratory experiments aimed at generating optically thick pair plasmas as well as for astrophysical models in which electron-positron pair plasmas play a relevant role.