Magnetized Decaying Turbulence in the Weakly Compressible Taylor-Green Vortex

TL;DR

This study uses ideal MHD simulations to analyze how magnetic fields influence turbulence in the Taylor-Green vortex, revealing magnetic dominance, altered energy spectra, and nonlocal energy transfers across scales.

Contribution

It provides new insights into magnetic energy dominance and nonlocal energy transfer mechanisms in weakly compressible magnetohydrodynamic turbulence.

Findings

Magnetic energy becomes dominant over kinetic energy across scales.

Energy spectra become shallower than $k^{-5/3}$ over time.

Nonlocal energy transfer from large-scale kinetic to small-scale magnetic energy.

Abstract

Magnetohydrodynamic turbulence affects both terrestrial and astrophysical plasmas. The properties of magnetized turbulence must be better understood to more accurately characterize these systems. This work presents ideal MHD simulations of the compressible Taylor-Green vortex under a range of initial sub-sonic Mach numbers and magnetic field strengths. We find that regardless of the initial field strength, the magnetic energy becomes dominant over the kinetic energy on all scales after at most several dynamical times. The spectral indices of the kinetic and magnetic energy spectra become shallower than $k^{-5/3}$ over time and generally fluctuate. Using a shell-to-shell energy transfer analysis framework, we find that the magnetic fields facilitate a significant amount of the energy flux and that the kinetic energy cascade is suppressed. Moreover, we observe nonlocal energy transfer from the large scale kinetic energy to intermediate and small scale magnetic energy via magnetic tension. We conclude that even in intermittently or singularly driven weakly magnetized systems, the dynamical effects of magnetic fields cannot be neglected.