Magnetic topologies of fully-convective dwarfs
J Morin, JF Donati, P Petit, T Forveille, X Delfosse, B Dintrans, W Dobler, L Albert

Abstract: Activity and magnetism is one of the most spectacular characteristics of low-mass stars like the Sun. Their magnetic fields are supposedly produced through dynamo processes involving turbulence and rotation, and operating in a thin interface layer located at the base of their outer convective envelope. Fully-convective dwarfs obviously lack such an interface layer, yet they are very active and strongly magnetic. This led theoreticians to propose that their fields were produced through exotic dynamo processes involving turbulence only, and whose mechanism is still subject to controversy. , , We will present the result of an ongoing ESPaDOnS program focussed on observing magnetic fields of fully-convective dwarfs. Since our initial result demonstrating that fully convective stars are able to trigger strong, large-scale, mainly-axisymmetric fields without the need for differential rotation, we initiated a small survey to investigate how the large-scale magnetic topology of fully-convective stars vary with stellar parameters such as mass and rotation rate. Preliminary results indicate that rotation rate likely plays a major role.