Numerical simulations of buoyancy instabilities in galaxy cluster plasmas with cosmic rays and anisotropic thermal conduction

TL;DR

This paper introduces a new numerical algorithm to simulate buoyancy instabilities in galaxy cluster plasmas influenced by cosmic rays and anisotropic thermal conduction, enabling more accurate modeling of these phenomena.

Contribution

The paper presents a novel numerical method that models cosmic rays as a fluid and incorporates anisotropic heat and cosmic-ray diffusion along magnetic field lines.

Findings

The algorithm accurately matches analytic eigenfunctions and growth rates.

It effectively simulates cosmic-ray driven buoyancy convection.

The method is applicable to various astrophysical and plasma physics contexts.

Abstract

In clusters of galaxies, the specific entropy of intracluster plasma increases outwards. Nevertheless, a number of recent studies have shown that the intracluster medium is subject to buoyancy instabilities due to the effects of cosmic rays and anisotropic thermal conduction. In this paper, we present a new numerical algorithm for simulating such instabilities. This numerical method treats the cosmic rays as a fluid, accounts for the diffusion of heat and cosmic rays along magnetic field lines, and enforces the condition that the temperature and cosmic-ray pressure remain positive. We carry out several tests to ensure the accuracy of the code, including the detailed matching of analytic results for the eigenfunctions and growth rates of linear buoyancy instabilities. This numerical scheme will be useful for simulating convection driven by cosmic-ray buoyancy in galaxy cluster plasmas and may also be useful for other applications, including fusion plasmas, the interstellar medium, and supernovae remnants.