It has been recognized that the magnetic flux observed on the solar surface appears first in low latitudes, and then this flux is gradually dispersed by super granular convective motions and meridional circulation. Theoretically, the magnetic flux transport could be explained by the interactions between magnetic fields and plasma flows on the solar surface through the theory of magnetohydrodynamics.
To understand this physical scenario, a quasi-three-dimensional, time-dependent, MHD model with differential rotation, meridional flow and effective diffusion as well as cyclonic turbulence effects is developed. Numerical experiments are presented for the study of Bipolar Magnetic Regions (BMRs). When the MHD effects are ignored, our model produced the classical results (Leighton, Astrophys. J., 146, 1547, 1964). The full model’s numerical results demonstrate that the interaction between magnetic fields and plasma flow (i.e., MHD effects), observed together with differential rotation and meridional flow, gives rise to the observed complexity of the evolution of BMRs.