Forced diffusion of solar magnetic fields

The observed latitude migration of solar magnetic features during the solar cycle is explained within the framework of a dynamic model employing subsurface horizontal forces. Consideration of the latitude distribution of the mean toroidal magnetic fields expected to be generated by differential rotation leads to the expectation of significant horizontal magnetic forces which tend to drive high-latitude features poleward and low-latitude features toward the equator. If this driving force is assumed to be resisted by the turbulent friction of solar material as well as by pressure forces, migration velocities can be estimated. The calculated drift rates agree quite well with the latitude drifts observed for sunspots, filaments, unipolar magnetic regions, and coronal features. This "forced diffusion" mechanism differs most significantly from the random-waW process in that it is dynamic rather than kinematic, Le., magnetic elements are systematically forced to the poles by the differential rotation itself. The overall estimated effectiveness of the mechanism indicates that it should be incorporated along with the random walk into solar dynamo models.