Magnetic fields in late-type dwarfs : preliminary results from a multiline approach.

Preliminary results of a multiline approach to the diagnosis of magnetic fields in late-type dwarfs are presented. The spectra of fours stars observed with the Coude Echelle Spectrometer of the European Southern Observatory are analyzed using the Stenflo-Lindegren technique, which permits empirical relations to be obtained between various parameters characterizing a statistical sample of observed line profiles and the atomic quantities pertaining to the corresponding transitions. These empirical relations are first tested on solar and stellar data and then interpreted with the help of a simple model of the line formation, and constraints on the magnetic field properties (mean strength, filling factor, thermodynamic properties of the magnetic regions compared to the nonmagnetic parts of the stellar surface) are derived.