Angular momentum transport in a contracting stellar radiative zone embedded in a large scale magnetic field

TL;DR

This paper investigates how large-scale magnetic fields influence angular momentum transport in contracting stellar radiative zones, potentially explaining stellar rotational evolution and magnetic dichotomies.

Contribution

It proposes a scenario where magnetic fields maintain solid-body rotation during contraction, then become unstable, leading to differential rotation and explaining observed stellar magnetic properties.

Findings

Large-scale magnetic fields can sustain solid-body rotation during stellar contraction.

An axisymmetric instability can disrupt magnetic fields, inducing differential rotation.

The model offers insights into the magnetic dichotomy in intermediate-mass stars.

Abstract

Some contracting or expanding stars are thought to host a large-scale magnetic field in their radiative interior. By interacting with the contraction-induced flows, such fields may significantly alter the rotational history of the star. They thus constitute a promising way to address the problem of angular momentum transport during the rapid phases of stellar evolution. In this work, we aim at studying the interplay between flows and magnetic fields in a contracting radiative zone. We propose a scenario that may account for the post-main sequence evolution of solar-like stars, in which a quasi-solid rotation can be maintained by a large-scale magnetic field during a contraction timescale. Then, an axisymmetric instability would destroy this large-scale structure and enables the differential rotation to set in. Such a contraction driven instability could also be at the origin of the observed dichotomy between strongly and weakly magnetic intermediate-mass stars.