Numerical Simulations of Driven Relativistic MHD Turbulence

TL;DR

This paper presents high-resolution numerical simulations of driven relativistic MHD turbulence, revealing magnetic energy growth, inertial scaling consistent with -5/3, and insights into velocity structure functions and magnetic field interactions in relativistic astrophysical flows.

Contribution

The study provides the first detailed numerical analysis of driven relativistic MHD turbulence, including spectral properties and velocity structure functions, in a weakly magnetized, mildly compressible relativistic fluid.

Findings

Magnetic energy saturates at about 1% of total energy.

Velocity power spectrum follows a -5/3 inertial scaling.

Velocity structures show weaker scale dependence than in non-relativistic flows.

Abstract

A wide variety of astrophysical phenomena involve the flow of turbulent magnetized gas with relativistic velocity or energy density. Examples include gamma-ray bursts, active galactic nuclei, pulsars, magnetars, micro-quasars, merging neutron stars, X-ray binaries, some supernovae, and the early universe. In order to elucidate the basic properties of the relativistic magnetohydrodynamical (RMHD) turbulence present in these systems, we present results from numerical simulations of fully developed driven turbulence in a relativistically warm, weakly magnetized and mildly compressible ideal fluid. We have evolved the RMHD equations for many dynamical times on a uniform grid with 1024^3 zones using a high order Godunov code. We observe the growth of magnetic energy from a seed field through saturation at about 1% of the total fluid energy. We compute the power spectrum of velocity and density-weighted velocity and conclude that the inertial scaling is consistent with a slope of -5/3. We compute the longitudinal and transverse velocity structure functions of order p up to 11, and discuss their possible deviation from the expected scaling for non-relativistic media. We also compute the scale-dependent distortion of coherent velocity structures with respect to the local magnetic field, finding a weaker scale dependence than is expected for incompressible non-relativistic flows with a strong mean field.