Suppression of Coronal Mass Ejections in active stars by an overlying large-scale magnetic field: A numerical study

TL;DR

This study uses 3D MHD simulations to demonstrate that a strong large-scale magnetic field can suppress coronal mass ejections in active stars, reducing their speed and confining eruptions within the stellar corona.

Contribution

It provides the first detailed numerical analysis of how large-scale magnetic fields influence CME suppression in active stars, extending solar CME models to stellar environments.

Findings

A 75 G dipolar magnetic field can fully confine CMEs.

CME kinetic energy suppression threshold is around 3×10^32 erg.

Erupting flares with energies above 6×10^32 erg can overcome magnetic confinement.

Abstract

We present results from a set of numerical simulations aimed at exploring the mechanism of coronal mass ejection (CME) suppression in active stars by an overlying large-scale magnetic field. We use a state-of-the-art 3D magnetohydrodynamic (MHD) code which considers a self-consistent coupling between an Alfv\'en wave-driven stellar wind solution, and a first-principles CME model based on the eruption of a flux-rope anchored to a mixed polarity region. By replicating the driving conditions used in simulations of strong solar CMEs, we show that a large-scale dipolar magnetic field of $75$ G is able to fully confine eruptions within the stellar corona. Our simulations also consider CMEs exceeding the magnetic energy used in solar studies, which are able to escape the large-scale magnetic field confinement. The analysis includes a qualitative and quantitative description of the simulated CMEs and their dynamics, which reveals a drastic reduction of the radial speed caused by the overlying magnetic field. With the aid of recent observational studies, we place our numerical results in the context of solar and stellar flaring events. In this way, we find that this particular large-scale magnetic field configuration establishes a suppression threshold around $\sim$$3 \times 10^{32}$~erg in the CME kinetic energy. Extending the solar flare-CME relations to other stars, such CME kinetic energies could be typically achieved during erupting flaring events with total energies larger than $6 \times 10^{32}$ erg (GOES class $\sim$X70).