On the effect of rotation on magnetohydrodynamic turbulence at high magnetic Reynolds number

TL;DR

This study uses 3D simulations to explore how rotation influences magnetohydrodynamic turbulence, revealing that rotation suppresses magnetic energy growth and alters flow structures in high magnetic Reynolds number conditions.

Contribution

The paper provides new insights into the effects of rotation on MHD turbulence at high magnetic Reynolds numbers through detailed numerical simulations.

Findings

Rotation prevents energy equipartition between kinetic and magnetic energies.

Decreasing Elsasser number reduces magnetic energy and energy transfer.

Flow structures show increased misalignment of velocity and magnetic fields with lower Elsasser numbers.

Abstract

This article is focused on the dynamics of a rotating electrically conducting fluid in a turbulent state. As inside the Earth's core or in various industrial processes, a flow is altered by the presence of both background rotation and a large scale magnetic field. In this context, we present a set of 3D direct numerical simulations of incompressible decaying turbulence. We focus on parameters similar to the ones encountered in geophysical and astrophysical flows, so that the Rossby number is small, the interaction parameter is large, but the Elsasser number, defining the ratio between Coriolis and Lorentz forces, is about unity. These simulations allow to quantify the effect of rotation and thus inertial waves on the growth of magnetic fluctuations due to Alfv\'en waves. Rotation prevents the occurrence of equipartition between kinetic and magnetic energies, with a reduction of magnetic energy at decreasing Elsasser number {\Lambda}. It also causes a decrease of energy transfer mediated by cubic correlations. In terms of flow structure, a decrease of {\Lambda} corresponds to an increase in the misalignment of velocity and magnetic field.