Rotation rate of the solar core as a key constraint to magnetic angular momentum transport in stellar interiors

TL;DR

This paper investigates how measuring the Sun's core rotation can constrain magnetic angular momentum transport models, showing that a faster core rotation supports certain magnetic instability theories and helps calibrate transport efficiency.

Contribution

It demonstrates that core rotation measurements can distinguish between different magnetic angular momentum transport prescriptions in stellar models.

Findings

Models with magnetic instabilities match observed surface velocities.

A faster solar core rotation supports the original Tayler-Spruit dynamo.

Core rotation measurements can calibrate transport efficiency independently.

Abstract

Context: The internal rotation of the Sun constitutes a fundamental constraint when modelling angular momentum transport in stellar interiors. In addition to the more external regions of the solar radiative zone probed by pressure modes, measurements of rotational splittings of gravity modes would offer an invaluable constraint on the rotation of the solar core. Aims: We study the constraints that a measurement of the core rotation rate of the Sun could bring on magnetic angular momentum transport in stellar radiative zones. Results: We first show that models computed with angular momentum transport by magnetic instabilities and a recent prescription for the braking of the stellar surface by magnetized winds can reproduce the observations of surface velocities of stars in open clusters. These solar models predict both a flat rotation profile in the external part of the solar radiative zone probed by pressure modes and an increase in the rotation rate in the solar core, where the stabilizing effect of chemical gradients plays a key role. A rapid rotation of the core of the Sun, as suggested by reported detections of gravity modes, is thus found to be compatible with angular momentum transport by magnetic instabilities. Moreover, we show that the efficiency of magnetic angular momentum transport in regions of strong chemical gradients can be calibrated by the solar core rotation rate independently from the unknown rotational history of the Sun. In particular, we find that a recent revised prescription for the transport of angular momentum by the Tayler instability can be easily distinguished from the original Tayler-Spruit dynamo, with a faster rotating solar core supporting the original prescription.