Fully resolved array of simulations investigating the influence of the magnetic Prandtl number on magnetohydrodynamic turbulence

TL;DR

This study uses high-resolution simulations to analyze how the magnetic Prandtl number affects energy dissipation and spectral transfer in magnetohydrodynamic turbulence, with implications for astrophysical and planetary phenomena.

Contribution

It provides a comprehensive, fully resolved numerical investigation of the magnetic Prandtl number's impact on MHD turbulence, correcting previous overestimations due to insufficient resolution.

Findings

Steepness of dissipation ratio scaling is overestimated in under-resolved simulations.

Nonhelical reverse spectral transfer occurs for Pm < 1.

Results are relevant for understanding magnetic phenomena in stars and planets.

Abstract

We explore the effect of the magnetic Prandtl number Pm on energy and dissipation in fully resolved direct numerical simulations of steady-state, mechanically forced homogeneous magnetohydrodynamic turbulence in the range Pm = 1/32 to 32. We compare the spectra and show that if the simulations are not fully resolved, the steepness of the scaling of the kinetic-to-magnetic dissipation ratio with Pm is overestimated. We also present results of decaying turbulence with helical and nonhelical magnetic fields, where we find nonhelical reverse spectral transfer for Pm < 1. The results of this systematic analysis have applications including stars, planetary dynamos, and accretion disks.