Zonal flows in a mean‐field solar dynamo model

Abstract Cyclic variations are observed in the solar differential rotation profile. The 11 year periodicity of these zonal shear flows (often referred to as “torsional oscillations”) is consistent with the idea that they are driven by the Lorentz forces that are associated with the large‐scale solar dynamo. This suggests that these flows may be able to provide indirect observational evidence that can be used to constrain solar dynamo models. This possibility is investigated by considering a simplified mean‐field dynamo model which incorporates the feedback of the large‐scale magnetic field upon the imposed velocity field. By specifying an unperturbed flow which mimics the solar differential rotation, it is shown that it is possible to reproduce most of the main qualitative features of the solar dynamo as well as a solar‐like pattern of zonal shear flows. The apparent success of this model has led to the investigation of several more subtle aspects of the problem, including the effects of stratification and long‐term modulation as well as the possible implications of the zonal shear flows that are observed at high latitudes. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)