Rotation profiles of solar-like stars with magnetic fields

TL;DR

This study models the rotation profiles of solar-like stars with magnetic fields, demonstrating that magnetic effects lead to nearly uniform radiative zone rotation and revealing transition regions with sharp angular velocity changes.

Contribution

It introduces a magnetic angular momentum transport coefficient and shows that magnetic fields can reproduce observed solar rotation profiles more accurately than purely hydrodynamic models.

Findings

Magnetic models match helioseismic angular momentum data within 3 sigma.

Rotation in the radiative zone is nearly uniform due to magnetic effects.

Transition regions with sharp angular velocity changes depend on stellar mass and age.

Abstract

The aim of this work is to investigate rotation profile of solar-like stars with magnetic fields. A diffusion coefficient of magnetic angular momentum transport is deduced. Rotating stellar models with different mass are computed under the effect of the coefficient. Then rotation profiles are obtained from the theoretical stellar models. The total angular momentum of solar model with only hydrodynamic instabilities is about 13 times larger than that of the Sun at the age of the Sun, and this model can not reproduce quasi-solid rotation in the radiative region. However, not only can the solar model with magnetic fields reproduce an almost uniform rotation in the radiative region, but its total angular momentum is consistent with helioseismic result at the level of 3 $\sigma$ at the age of the Sun. The rotation of solar-like stars with magnetic fields is almost uniform in the radiative region. But there is an obvious transition region of angular velocity between the convective core and the radiative region of models with 1.2 - 1.5 $M_{\odot}$, where angular velocity has a sharp radial change, which is different from the rotation profile of the Sun and massive stars with magnetic fields. Moreover the changes of the angular velocity in the transition region increase with the increasing in the age and mass.