Towards understanding dynamo action in M dwarfs

TL;DR

This paper explores the connection between observational magnetic activity in M dwarfs and dynamo theory, proposing configurations and tests to better understand stellar magnetic phenomena in these stars.

Contribution

It introduces four magnetic configurations relevant to M dwarfs based on dynamo theory and suggests observational tests to identify them, advancing the theoretical and observational link.

Findings

Models predict high-latitude surface magnetic activity in M dwarfs.

Identification of magnetic configurations involves substantial uncertainties.

Long-term Zeeman-Doppler imaging is essential for progress.

Abstract

Recent progress in observational studies of magnetic activity in M dwarfs urgently requires support from ideas of stellar dynamo theory. We propose a strategy to connect observational and theoretical studies. In particular, we suggest four magnetic configurations that appear relevant to dwarfs from the viewpoint of the most conservative version of dynamo theory, and discuss observational tests to identify the configurations observationally. As expected, any such identification contains substantial uncertainties. However the situation in general looks less pessimistic than might be expected. Several identifications between the phenomenology of individual stars and dynamo models are suggested. Remarkably, all models discussed predict substantial surface magnetic activity at rather high stellar latitudes. This prediction looks unexpected from the viewpoint of our experience observing the Sun (which of course differs in some fundamental ways from these late-type dwarfs). We stress that a fuller understanding of the topic requires a long-term (at least 15 years) monitoring of M dwarfs by Zeeman-Doppler imaging.