The magnetic field pattern associated with large scale convective motions, which are much larger than the supergranules and have been conceived as a source of maintenance of the solar differential rotation, is calculated in the framework Of a slowly and differentially rotating thin spherical shell, including the effects of thermal conductivity and viscosity. The approximations of Boussinesq are used and the initial state of the magnetic field is assumed to be purely toroidal.
The resulting magnetic field pattern rotates rigidly on the differentially rotating Sun with some phase delay to the convective pattern, if it is assumed that only the predominant mode with the maximum growth rate is actually realized in the solar convection zone. The obtained magnetic and convective patterns and their properties seem to explain naturally the various aspects of large scale ordering of solar activity such as the existence and behavior of complexes of activity, the rigid body rotation of proton flare active longitudes, their association with UMR's, the existence of ghost and mirror image of UMR's themselves and the fact that the rotational period derived from sunspot data is shorter than that derived spectroscopically from fluid velocity.