Nonlinear Dynamics of Magnetic Islands Imbedded in Small-Scale Turbulence

TL;DR

This paper investigates the complex nonlinear behavior of magnetic islands within small-scale turbulence using a reduced magnetohydrodynamic model, revealing how pressure gradients influence instability phases and island dynamics.

Contribution

It introduces a numerical analysis of magnetic island dynamics in turbulence, highlighting the role of pressure gradients and secondary instabilities in shaping nonlinear interactions.

Findings

Pressure gradients control linear and nonlinear tearing phases.

Secondary instabilities can induce poloidal rotation of islands.

Nonlocal interactions involve small-scale turbulence effects.

Abstract

The nonlinear dynamics of magnetic tearing islands imbedded in a pressure gradient driven turbulence is investigated numerically in a reduced magnetohydrodynamic model. The study reveals regimes where the linear and nonlinear phases of the tearing instability are controlled by the properties of the pressure gradient. In these regimes, the interplay between the pressure and the magnetic flux determines the dynamics of the saturated state. A secondary instability can occur and strongly modify the magnetic island dynamics by triggering a poloidal rotation. It is shown that the complex nonlinear interaction between the islands and turbulence is nonlocal and involves small scales.