Weak- and strong-field dynamos: from the Earth to the stars

Julien Morin¹ Emmanuel Dormy² Martin Schrinner² Jean-François Donati³

¹ Dublin Institute for Advanced Studies, School of Cosmic Physics, 31 Fitzwilliam Place, Dublin 2, Ireland
² MAG (ENS/IPGP), LRA, Ecole Normale Supérieure, 24 Rue Lhomond, 75252 Paris Cedex 05, France
³ IRAP-UMR 5277, CNRS & Univ. de Toulouse, 14 Av. E. Belin, F-31400 Toulouse, France

MNRAS, Volume 418, Issue 1, pages L133-L137, November 2011.

Keywords: dynamo; planets and satellites: magnetic fields; stars: low-mass; stars: magnetic field

Abstract. Observations of magnetism in very low mass stars recently made important progress, revealing characteristics that are now to be understood in the framework of dynamo theory. In parallel, there is growing evidence that dynamo processes in these stars share many similarities with planetary dynamos. We investigate the extent to which the weak-field versus strong-field bistability predicted for the geodynamo can apply to recent observations of two groups of very low mass fully-convective stars sharing similar stellar parameters but generating radically different types of magnetic fields. Our analysis is based on previously published spectropolarimetric and spectroscopic data. We argue that these can be interpreted in the framework of weak- and strong-field dynamos.