Mode selection mechanism and magnetic diffusivity in a non-axisymmetric solar dynamo model

The generation of solar non-axisymmetric magnetic fields is studied based on a linear alpha(2)-Omega dynamo model in a rotating spherical frame. The model consists of a solar-like differential rotation, a magnetic diffusivity varied with depth, and three types of a-effects with different locations, i.e. the tachocline, the whole convective zone and the sub-surface. Some comparisons of the critical a-values of axi-symmetric (m = 0) and longitude-dependent modes (in = 1,2,3) are presented to show the roles of the magnetic diffusivity in the problem of modes selection. With the changing of diffusivity intensity for the given solar differential rotation system, the dominant mode possibly changes likewise and the stronger the diffusivity is, the easier the non-axisymmetric modes are excited. The influence of the diffusivity and differential rotation on the configurations of the dominant modes are also presented. (c) 2007 COSPAR. Published by Elsevier Ltd. All rights reserved.