Enhanced dynamo drive for the sawtooth relaxation process due to non-uniform resistivity distribution in a reversed field pinch

TL;DR

This study uses 3D resistive MHD simulations to show that non-uniform resistivity enhances the dynamo effect and accelerates the sawtooth relaxation process in reversed field pinch plasmas.

Contribution

It demonstrates that resistivity inhomogeneity significantly boosts the dynamo effect and modifies the sawtooth process in RFPs, using realistic simulation profiles.

Findings

Resistivity inhomogeneity accelerates magnetic flux diffusion.

Enhanced dynamo effect due to non-uniform resistivity.

Altered self-sustained reversal state in RFP plasma.

Abstract

In this work, we use the three-dimensional resistive MHD code NIMROD to investigate the impact of resistivity inhomogeneity on the sawtooth process of an reversed field pinch (RFP) plasma. The simulation employs a non-uniform resistivity profile similar to experiments, which monotonically increases from the core to the edge as the temperature decreases. The resistivity inhomogeneity introduces an additional electric field in the plasma, which accelerates the inward diffusion of magnetic flux and changing the self sustained reversal state, hence significantly enhances the dynamo effect and the sawtooth process in the RFP plasma.