Ejections of magnetic structures above a spherical wedge driven by a convective dynamo with differential rotation

TL;DR

This study models magnetic field emergence and ejections in a spherical wedge with a convective dynamo, revealing irregular magnetic ejections that resemble solar coronal mass ejections, using a simplified stellar atmosphere simulation.

Contribution

It extends previous models by combining a convective dynamo with a nearly isothermal corona in a spherical wedge to study magnetic ejections.

Findings

Magnetic fields emerge at the surface and are ejected into the corona.

Ejections occur irregularly and are weaker than in earlier models.

Some ejections are tentatively linked to solar coronal mass ejections.

Abstract

We combine a convectively driven dynamo in a spherical shell with a nearly isothermal density-stratified cooling layer that mimics some aspects of a stellar corona to study the emergence and ejections of magnetic field structures. This approach is an extension of earlier models, where forced turbulence simulations were employed to generate magnetic fields. A spherical wedge is used which consists of a convection zone and an extended coronal region to $\approx1.5$ times the radius of the sphere. The wedge contains a quarter of the azimuthal extent of the sphere and $150\degr$ in latitude. The magnetic field is self-consistently generated by the turbulent motions due to convection beneath the surface. Magnetic fields are found to emerge at the surface and are ejected to the coronal part of the domain. These ejections occur at irregular intervals and are weaker than in earlier work. We tentatively associate these events with coronal mass ejections on the Sun, even though our model of the solar atmosphere is rather simplistic.