The Role of MHD in the ICM and its Interactions with AGN Outflows

TL;DR

This paper reviews the influence of magnetic fields on the intracluster medium (ICM) and their interactions with active galactic nuclei (AGN) outflows, emphasizing microscopic effects and magnetic tension in high-beta plasmas.

Contribution

It explores the applicability of magnetohydrodynamics (MHD) in the ICM despite large Coulomb mean free paths, highlighting the roles of microscopic effects and magnetic tension.

Findings

Magnetic fields influence ICM dynamics mainly through microscopic effects and magnetic tension.

MHD models can still be relevant in the ICM despite large Coulomb mean free paths.

Magnetic fields contribute to the thermodynamics and interactions in the ICM.

Abstract

Magnetic fields probably play a central role in the dynamics and thermodynamics of ICMs and their interactions with AGNs, despite the fact that the fields usually contribute relatively little pressure; i.e., the ICM is a ``high-$\beta$'' plasma. More typically, the roles of magnetic fields come through ``microscopic'' influences on charged particle behaviors, and through magnetic tension, which can still be significant in subsonic, high-$\beta$ flows. I briefly review these issues, while exploring the underlying question of using the commonly-applied magnetohydrodynamics model in the ICM when Coulomb scattering mean free paths can sometimes exceed tens of kiloparsecs.