Destabilization mechanism of the collisional microtearing mode in magnetized slab plasmas

TL;DR

This paper investigates how electron collisions destabilize the microtearing mode in magnetized slab plasmas, revealing the underlying mechanism and its relevance to experiments, with nonlinear simulations showing no magnetic reconnection.

Contribution

It provides a theoretical and simulation-based analysis of the collisional destabilization mechanism of microtearing modes, including a comprehensive collision model.

Findings

Identifies the lag of the parallel electric field as the destabilization mechanism.

Quantifies the effects of collisions on mode stability.

Shows microtearing mode does not cause magnetic reconnection in nonlinear simulations.

Abstract

The destabilization mechanism of the collisional microtearing mode driven by an electron temperature gradient is studied using theoretical analyses and gyrokinetic simulations including a comprehensive collision model, in magnetized slab plasmas. The essential destabilization mechanism of the microtearing mode is the lag of the parallel inductive electric field behind the magnetic field owing to the time-dependent thermal force and inertia force induced by the velocity-dependent electron--ion collisions. Quantitative measurements of the collision effects enable us to identify the unstable regime against collisionality and reveal the relevance of the collisional microtearing mode with existing toroidal experiments. A nonlinear simulation demonstrates that the microtearing mode does not drive magnetic reconnection with the explosive release and conversion of the magnetic energy.