2-D Magnetohydrodynamic Simulations of Induced Plasma Dynamics in the Near-Core Region of a Galaxy Cluster

TL;DR

This study uses 2-D resistive MHD simulations to investigate plasma dynamics and thermal processes in the core of galaxy cluster A2199, highlighting the limited role of thermal conduction and the significance of initial plasma conditions.

Contribution

It demonstrates the effects of anisotropic thermal conduction and initial plasma density on cooling in galaxy clusters, and explores the impact of non-hydrostatic conditions on plasma evolution.

Findings

Thermal conduction is ineffective in preventing catastrophic cooling.

Initial plasma density critically influences simulation outcomes.

Pressure work can dominate energy evolution under non-equilibrium conditions.

Abstract

We present results from numerical simulations of the cooling-core cluster A2199 produced by the two-dimensional (2-D) resistive magnetohydrodynamics (MHD) code MACH2. In our simulations we explore the effect of anisotropic thermal conduction on the energy balance of the system. The results from idealized cases in 2-D axisymmetric geometry underscore the importance of the initial plasma density in ICM simulations, especially the near-core values since the radiation cooling rate is proportional to ${n_e}^2$. Heat conduction is found to be non-effective in preventing catastrophic cooling in this cluster. In addition we performed 2-D planar MHD simulations starting from initial conditions deliberately violating both thermal balance and hydrostatic equilibrium in the ICM, to assess contributions of the convective terms in the energy balance of the system against anisotropic thermal conduction. We find that in this case work done by the pressure on the plasma can dominate the early evolution of the internal energy over anisotropic thermal conduction in the presence of subsonic flows, thereby reducing the impact of the magnetic field. Deviations from hydrostatic equilibrium near the cluster core may be associated with transient activity of a central active galactic nucleus and/or remnant dynamical activity in the ICM and warrant further study in three dimensions.