Magnetoclinicity Instability

TL;DR

This paper introduces the concept of magnetoclinicity, an effect in compressible MHD turbulence where density gradients influence magnetic field generation, leading to large-scale instabilities.

Contribution

It identifies and analyzes the magnetoclinicity effect as a new mechanism for magnetic field instability in astrophysical turbulent flows.

Findings

Magnetoclinicity causes large-scale magnetic field destabilization.

Density variance mediates the electromotive force in turbulence.

Instability occurs near strong mean density gradients.

Abstract

In strongly compressible magnetohydrodynamic turbulence, obliqueness between the large-scale density gradient and magnetic field gives an electromotive force mediated by density variance (intensity of density fluctuation). This effect is named ``magnetoclinicity'', and is expected to play an important role in large-scale magnetic-field generation in astrophysical compressible turbulent flows. Analysis of large-scale instability due to the magnetoclinicity effect shows that the mean magnetic-field perturbation is destabilised at large scales in the vicinity of strong mean density gradient in the presence of density variance.