On the linear stability of collisionless microtearing modes

TL;DR

This paper investigates the linear stability of collisionless microtearing modes in fusion plasmas, revealing their potential occurrence in low-collisionality regimes relevant for future fusion devices like spherical tokamaks.

Contribution

It demonstrates that collisionless microtearing instabilities can occur under certain conditions, challenging the current belief that they require finite collisionality.

Findings

Collisionless microtearing modes can be unstable in low-collisionality regimes.

Relevance to reversed field pinches and spherical tokamaks.

Use of gyrokinetic and drift-kinetic approaches for analysis.

Abstract

Microtearing modes are an important drive of turbulent heat transport in present-day fusion plasmas. We investigate their linear stability under very-low collisionality regimes, expected for the next generations of devices, using gyrokinetic and drift-kinetic approaches. At odds with current opinion, we show that collisionless microtearing instabilities may occur in certain experimental conditions, particularly relevant for such devices as reversed field pinches and spherical tokamaks.