On the influence of magnetic helicity on X-rays emission of solar and stellar coronae

TL;DR

This study uses 3D MHD simulations to show that increased magnetic helicity in solar-like stars leads to higher coronal temperatures and X-ray emissions, scaling cubically with helicity.

Contribution

It demonstrates a quantitative relationship between magnetic helicity and X-ray emission, linking stellar rotation, magnetic helicity, and coronal activity.

Findings

X-ray emission increases cubically with magnetic helicity.

Higher magnetic helicity results in higher coronal temperatures.

Stellar rotation influences X-ray emission via magnetic helicity production.

Abstract

Observation of solar-like stars show a clear relation between X-ray emission and their rotation. Higher stellar rotation can lead to a larger magnetic helicity production in stars. We aim to understand the relation between magnetic helicity on the surface of a star to their coronal X-ray emission. We use 3D MHD simulations to model the corona of the solar-like stars. We take an observed magnetogram as in photospheric activity input, and inject different values of magnetic helicity. We use synthesis emission to calculate the X-ray emission flux of each simulation and investigate how this scales with injected magnetic helicity. We find that for larger injected magnetic helicities an increase in temperature and an increase in X-ray emission. The X-ray emission scaled cubicly with the injected helicity. We can related this to increase of horizontal magnetic field and therefore higher Poynting flux at the coronal base. Using typical scaling of magnetic helicity production with stellar rotation, we can explain the increase of X-ray emission with rotation only by an increase of magnetic helicity at the surface of a star.