Simulations of Weakly Magnetized Turbulent Mixing Layers

TL;DR

This study uses 3D MHD simulations to show that even weak magnetic fields can significantly influence turbulent mixing layers by reducing hot gas inflow and altering phase structures, impacting cold gas survival.

Contribution

It provides the first detailed analysis of magnetic field effects on turbulent mixing layers in a multiphase astrophysical context, highlighting magnetic suppression mechanisms.

Findings

Weak magnetic fields amplify and reduce hot gas surface brightness.

Magnetic pressure support suppresses turbulent mixing.

Results are resolution-converged and independent of thermal conduction.

Abstract

Radiative turbulent mixing layers are expected to form pervasively at the phase boundaries in multiphase astrophysical systems. This inherently small scale structure is dynamically crucial because it directly regulates the mass, momentum and energy exchanges between adjacent phases. Previous studies on hydrodynamic turbulent mixing layers have revealed the interactions between cold and hot phases in the context of the circumgalactic medium, offering important insight into the fate of cold clouds traveling through hot galactic winds. However, the role of magnetic field has only been sparsely investigated. We perform a series of 3D magnetohydrodynamics (MHD) simulations of such mixing layers in the presence of weak to modest background magnetic field. We find that due to field amplification, even relatively weak background magnetic fields can significantly reduce the surface brightness and inflow velocity of the hot gas in the mixing layer. This reduction is attributed to a combination of magnetic pressure support and direct suppression of turbulent mixing, both of which alter the phase structures. Our results are largely independent of thermal conduction and converged with resolution, offering insights on the survival of cold gas in multiphase systems.