Effect of current corrugations on the stability of the tearing mode

TL;DR

This paper investigates how small stationary current corrugations in fusion plasmas influence tearing mode stability, providing a scaling law that explains the triggering of neoclassical tearing modes without major MHD activity.

Contribution

It introduces a simple scaling law linking current corrugations to tearing mode stability, offering a new explanation for NTM triggers in fusion plasmas.

Findings

Current corrugations can destabilize tearing modes.

A scaling law predicts the impact of current corrugations on stability.

The mechanism explains NTM triggers without significant MHD activity.

Abstract

The generation of zonal magnetic fields in laboratory fusion plasmas is predicted by theoretical and numerical models and was recently observed experimentally. It is shown that the modification of the current density gradient associated with such corrugations can significantly affect the stability of the tearing mode. A simple scaling law is derived that predicts the impact of small stationary current corrugations on the stability parameter $\Delta'$. The described destabilization mechanism can provide an explanation for the trigger of the Neoclassical Tearing Mode (NTM) in plasmas without significant MHD activity.