Characterizing the feedback of magnetic field on the differential rotation of solar-like stars

TL;DR

This study investigates how magnetic fields influence the differential rotation of solar-like stars, revealing that magnetic effects weaken the rotation trend and align better with observations, with different angular momentum transport mechanisms for prograde and retrograde cases.

Contribution

It provides the first detailed analysis of magnetic field impacts on differential rotation trends across various stellar rotation rates and masses using 3D dynamo simulations.

Findings

Magnetic fields weaken the differential rotation trend compared to hydrodynamic models.

Prograde and retrograde rotations show opposite angular momentum transport patterns.

Thermal wind balance is maintained in prograde cases, while Reynolds stresses dominate in retrograde cases.

Abstract

The aim of this article is to study how the differential rotation of solar-like stars is influenced by rotation rate and mass in presence of magnetic fields generated by a convective dynamo. We use the ASH code to model the convective dynamo of solar-like stars at various rotation rates and masses, hence different effective Rossby numbers. We obtained models with either prograde (solar-like) or retrograde (anti-solar-like) differential rotation. The trends of differential rotation versus stellar rotation rate obtained for simulations including the effect of the magnetic field are weaker compared with hydro simulations ($\Delta \Omega \propto (\Omega/\Omega_{\odot})^{0.44}$ in the MHD case and $\Delta \Omega \propto (\Omega/\Omega_{\odot})^{0.89}$ in the hydro case), hence showing a better agreement with the observations. Analysis of angular momentum transport revealed that the simulations with retrograde and prograde differential rotation have opposite distribution of the viscous, turbulent Reynolds stresses and meridional circulation contributions. The thermal wind balance is achieved in the prograde cases. However, in retrograde cases Reynolds stresses are dominant for high latitudes and near the top of the convective layer. Baroclinic effects are stronger for faster rotating models.