THE SOLAR DYNAMO WITH MERIDIONAL CIRCULATION

We show that meridional circulation can have a profound influence on d ynamo models for the solar cycle. Motivated by the observed tilt angle s of sunspot groups we assume that the generation of the poloidal fiel d takes place near the surface, while a shear layer of radial differen tial rotation produces the toroidal field at the bottom of the convect ion zone. Both layers are coupled by a circulation with a poleward dir ected flow in the upper part and an equatorward flow in the deep layer s of the convection zone. The circulation forces the toroidal field be lts (which are responsible for the surface activity) to move equatorwa rd. This leads to butterfly diagrams in qualitative agreement with the observations, even if the dynamo wave would propagate poleward in the absence of circulation. This result opens the possibility to construc t models for the solar cycle which are based on observational data (ti lt angles, differential rotation, and meridional circulation).