What controls the magnetic geometry of M dwarfs

摘要: Context. Observations of rapidly rotating M dwarfs show a broad variety large-scale magnetic fields encompassing dipoledominated and multipolar geometries. In dynamo models, the relative importance inertia in force balance, which is quantified by local Rossby number, known to have strong impact on field geometry. Aims. We aim assess relevance number controlling geometry dwarfs. Methods. explored similarities between anelastic models spherical shells observations active M-dwarfs, focusing geometries derived from spectropolarimetric studies. To do so, we constructed observation-based quantities aimed reflect diagnostic parameters employed numerical models. Results. The transition dipole-dominated early mid tentatively attributed threshold. interpret late magnetism result bistability occurring at low number. By analogy with expect different amplitudes differential rotation two branches.