Differential rotation and magnetic fields in stellar interiors

TL;DR

This paper reviews the processes affecting magnetic field evolution in differentially rotating stars, focusing on instabilities, diffusion effects, and the open questions about stable magnetic equilibria.

Contribution

It provides a comprehensive review of instabilities and diffusion effects influencing magnetic fields in stellar interiors, highlighting the initial dominance of pinch-type instability.

Findings

Pinch-type instability is the first to develop in stellar magnetic fields.

Thermal and magnetic diffusion significantly influence instability behavior.

The evolution of strong magnetic fields and the existence of stable equilibria remain open questions.

Abstract

The processes contributing to the evolution of an initially weak magnetic field in a differentially rotating star are reviewed. These include rotational smoothing (akin to convective expulsion) and a list of about 5 instabilities, among them magnetorotational instability, byoyancy instability, and pinch-type instabilities. The important effects of thermal and magnetic diffusion on these instabilities are analyzed in some detail. The first instability to set in is a pinch-type instability. It becomes important in modifying the field configuration before magnetic buoyancy-driven instabilities set in. The evolution of an initially strong field remains a more open question, including the old problem whether dynamically stable magnetic equilibria exist in stars.