Stellar Coronal Response to Differential Rotation and Flux Emergence

TL;DR

This study uses numerical simulations to explore how differential rotation and flux emergence influence a star's magnetic field and coronal activity, finding flux emergence has a more significant impact than differential rotation.

Contribution

It introduces a coupled flux transport and magnetofrictional model to analyze the effects of flux emergence and differential rotation on stellar coronae, highlighting the dominant role of flux emergence.

Findings

Flux emergence significantly increases coronal magnetic energy and flux.

Differential rotation makes the corona more open and non-potential.

Flux emergence rate correlates with increased coronal activity.

Abstract

We perform a numerical parameter study to determine what effect varying differential rotation and flux emergence has on a star's non-potential coronal magnetic field. In particular we consider the effects on the star's surface magnetic flux, open magnetic flux, mean azimuthal field strength, coronal free magnetic energy, coronal heating and flux rope eruptions. To do this, we apply a magnetic flux transport model to describe the photospheric evolution, and couple this to the non-potential coronal evolution using a magnetofrictional technique. A flux emergence model is applied to add new magnetic flux onto the photosphere and into the corona. The parameters of this flux emergence model are derived from the solar flux emergence profile, however the rate of emergence can be increased to represent higher flux emergence rates than the Sun's. Overall we find that flux emergence has a greater effect on the non-potential coronal properties compared to differential rotation, with all the aforementioned properties increasing with increasing flux emergence rate. Although differential rotation has a lesser effect on the overall coronal properties compared to flux emergence, varying differential rotation does alter the coronal structure. As the differential rotation rate increases, the corona becomes more open, and more non-potential.