Single-hemisphere dynamos in M-dwarf stars

TL;DR

This study explores magnetic dynamo processes in fully convective M-dwarf stars using advanced simulations, revealing hemispheric magnetic fields that could impact exoplanet environments and stellar evolution.

Contribution

First simulation study of dynamo action in stratified, rotating fully convective M-dwarfs capturing full star geometry, discovering hemispheric magnetic field states.

Findings

Hemispheric-dynamo states with global magnetic fields confined to one hemisphere.

Implications for exoplanet habitability and stellar spindown due to hemispheric magnetic fields.

Surprising dynamo behaviors differing from previous models.

Abstract

M-dwarf stars below a certain mass are convective from their cores to their photospheres. These fully convective objects are extremely numerous, very magnetically active, and the likely hosts of many exoplanets. Here we study, for the first time, dynamo action in simulations of stratified, rotating fully convective M-dwarf stars. Importantly, we use new techniques to capture the correct full ball geometry down to the center of the star. We find surprising dynamo states in these systems, with the global-scale mean fields confined strongly to a single hemisphere, in contrast to prior stellar dynamo solutions. These hemispheric-dynamo stars are likely to have profoundly different interactions with their surroundings, with important implications for exoplanet habitability and stellar spindown.