On the Effect of Magnetic Spots on Stellar Winds and Angular Momentum Loss

TL;DR

This study uses simulations to explore how star spot locations and magnetic field strengths influence stellar wind structures and angular momentum loss, revealing a complex interplay affecting stellar evolution.

Contribution

It introduces a detailed MHD simulation approach to analyze the impact of spot latitudes and magnetic field strength on stellar wind and angular momentum loss.

Findings

Spot location significantly alters wind structure.

Angular momentum loss depends on spot latitude and plasma density.

Feedback mechanisms may link magnetic field distribution and stellar dynamos.

Abstract

We simulate the effect of latitudinal variations in the location of star spots, as well as their magnetic field strength, on stellar angular momentum loss to the stellar wind. We use the Michigan solar corona global MagnetoHydroDynamic model, which incorporates realistic relation between the magnetic field topology and the wind distribution. We find that the spots location significantly affects the stellar wind structure, and as a result, the total mass loss rate and angular momentum loss rate. In particular, we find that the angular momentum loss rate is controlled by the mass flux when spots are located at low latitudes but is controlled by an increased plasma density between the stellar surface and the Alfven surface when spots are located at high latitudes. Our results suggest that there might be a feedback mechanism between the magnetic field distribution, wind distribution, angular momentum loss through the wind, and the motions at the convection zone that generate the magnetic field. This feedback might explain the role of coronal magnetic fields in stellar dynamos.