Magnetic Field Amplification by Turbulence in A Relativistic Shock Propagating through An Inhomogeneous Medium

TL;DR

This study uses 2D relativistic MHD simulations to show how turbulence in inhomogeneous media can significantly amplify magnetic fields in relativistic shocks, with implications for astrophysical phenomena.

Contribution

It demonstrates magnetic field amplification via turbulence in relativistic shocks through detailed simulations, highlighting the effects of inhomogeneity and magnetic field orientation.

Findings

Magnetic fields are strongly amplified in turbulent postshock regions.

The magnetic energy spectrum is flatter than Kolmogorov, indicating small-scale dynamo action.

Amplification depends on the preshock magnetic field direction and shock strength.

Abstract

We perform two-dimensional relativistic magnetohydrodynamic simulations of a mildly relativistic shock propagating through an inhomogeneous medium. We show that the postshock region becomes turbulent owing to preshock density inhomogeneity, and the magnetic field is strongly amplified due to the stretching and folding of field lines in the turbulent velocity field. The amplified magnetic field evolves into a filamentary structure in two-dimensional simulations. The magnetic energy spectrum is flatter than the Kolmogorov spectrum and indicates that a so-called small-scale dynamo is occurring in the postshock region. We also find that the amount of magnetic-field amplification depends on the direction of the mean preshock magnetic field, and the time scale of magnetic-field growth depends on the shock strength.