Circulation-dominated solar shell dynamo models with positive alpha-effect

We present shell dynamo models for the solar convection zone with positive alpha -effect in the northern hemisphere and a meridional circulation which is directed equatorward at the bottom and poleward at the top of the convection zone. Two different rotation patterns are used: a simple variation of the rotation rate with depth and the rotation law as derived by helioseismology. Depending on the Reynolds number associated with the meridional ow, the dynamo shows a whole zoo of solutions. For sufficiently small values of the eddy magnetic diffusivity (10(11) cm(2)/s), field advection by the meridional ow becomes dominant and even changes the character of the butterfly diagram. Flow amplitudes of a few m/s are then sufficient to turn the originally wrong butterfly diagram into a solar-type butterfly diagram, i.e. with activity belts drifting equatorward. This effect can easily be demonstrated with a super-rotation law (partial derivative Omega/partial derivativer > 0) with Omega independent of the latitude. The situation is much more complicated for the real rotation law with the observed strong negative shear at high latitudes. With zero meridional ow, oscillating solutions are found without any latitudinal migration of the toroidal field belts, neither poleward nor equatorward. Small but finite ow amplitudes cause the magnetic field belts to drift poleward while in case of fast ow they move equatorward.