The Large-Scale Axisymmetric Magnetic Topology of a

Understanding how cool stars produce magnetic fields within their interiors is crucial for predicting the impact of such fields, such as the activity cycle of the Sun. In this respect, studying fully convective stars enables us to investigate the role of convective zones in magnetic field generation. We produced a magnetic map of a rapidly rotating, very-low-mass, fully convective dwarf through tomographic imaging from time series of spectropolarimetric data. Our results, which demonstrate that fully convective stars are able to trigger axisymmetric large-scale poloidal fields without differential rotation, challenge existing theoretical models of field generation in cool stars. M agnetic fields of cool stars are supposedly produced and sustained through dynamo processes operat-ing in their outer convective envelopes and involving both differential rotation and tur-bulence (1). Differential rotation winds up an initially poloidal field, generating a toroida