NONAXISYMMETRIC DYNAMO SOLUTIONS AND EXTENDED STARSPOTS ON LATE-TYPE STARS

We have computed mean field dynamo models in a deep spherical shell, without restriction on spatial symmetries, in which the growth of the magnetic field is limited solely by the back reaction of the large scale Lorentz force on the large scale motions. A parameterization of the Reynolds stress tenser is included to describe the generation of differential rotation. We find for moderate values of the Taylor number, when the differential rotation is also small, that the stable magnetic fields are nonaxisymmetric, with the same basic topology as a 'perpendicular dipole'. For larger Taylor numbers, and stronger absolute differential rotation, we expect axisymmetric fields to be stable. We briefly discuss the relevance of our results to the large scale nonaxisymmetric structures and extended starspots observed on late type 'active giant' and other stars.