A time-dependent solution of transonic, tran-Alfvenic MHD flow in the solar meridian

A time-dependent method and a practical differentiating scheme, concerning both fluid and magnetic field in the solar meridian, have been developed to obtain the transonic, tran-Alfvenic solution for background solar wind with the formation of heliospheric current sheet. The so-called projected-characteristic boundary condition in spherical coordinate is further studied and successfully used at the inner and outer boundaries. It is shown that a closed magnetic field is drawn outward by the expanding solar wind and changes gradually into the quasi-helmet-type. The interaction between the fluid and magnetic fields is identical with some supposed mechanism of the corona. The simulation results also show the possible distributions of the dynamic and magnetic parameters in the solar meridian.