Oblique tearing mode instability: guide field and Hall effect

TL;DR

This paper analyzes the linear stability of tearing mode instability in current sheets with guide fields and Hall effects, revealing how these factors influence mode growth, wave dispersion, and eigen-function structure in astrophysical plasmas.

Contribution

It provides a detailed linear stability analysis of tearing modes considering guide fields and Hall effects, highlighting their impact on mode behavior and structure.

Findings

Strong guide fields do not alter the fastest growing mode in 2D wave vector space.

Hall effect causes the guide field to induce dispersive wave propagation.

Strong guide fields suppress oblique mode structures and induce asymmetry in eigen-functions.

Abstract

The tearing mode instability is one important mechanism that may explain the triggering of fast magnetic reconnection in astrophysical plasmas such as the solar corona and the Earth's magnetosphere. In this paper, the linear stability analysis of the tearing mode is carried out for a current sheet in the presence of a guide field, including the Hall effect. We show that the presence of a strong guide field does not modify the most unstable mode in the two-dimensional wave vector space orthogonal to the current gradient direction, which remains the fastest growing parallel mode. With the Hall effect, the inclusion of a guide field turns the non-dispersive propagation along the guide field direction to a dispersive one. The oblique modes have a wave-like structure along the normal direction of the current sheet and a strong guide field suppresses this structure while making the eigen-functions asymmetric.