Influence of tearing instability on magnetohydrodynamic turbulence

TL;DR

This paper investigates how tearing instability influences magnetohydrodynamic turbulence, providing numerical evidence that a new turbulence regime can form below a critical scale where tearing effects dominate.

Contribution

It offers the first numerical demonstration that tearing instability can compete with nonlinear evolution in anisotropic MHD turbulence, supporting the existence of a tearing-mediated turbulence regime.

Findings

Tearing instability can compete with nonlinear evolution in 2D MHD turbulence.

A new tearing-mediated regime of turbulence can exist below a critical scale.

Numerical results support the transition to a tearing-influenced turbulence regime.

Abstract

It has been proposed recently by Loureiro & Boldyrev [Phys. Rev. Lett. 118, 245101 (2017)] and Mallet et al. [Mon. Not. R. Astron. Soc. 468, 4862 (2017)] that strongly anisotropic current sheets formed in the inertial range of magnetohydrodynamic turbulence become affected by the tearing instability at scales smaller than a critical scale $\lambda_\mathrm{c}$, and larger than the dissipation scale of turbulence. If true, this process can modify the nature of energy cascade at smaller scales, leading to a new, tearing-mediated regime of magnetohydrodynamic (MHD) turbulence. In this work we present a numerical study of strongly anisotropic, two-dimensional turbulent eddies, and we demonstrate that the tearing instability can indeed compete with their nonlinear evolution. The results, therefore, provide direct numerical support for the picture that a new regime of MHD turbulence can exist below $\lambda_\mathrm{c}$.