A GLOBAL NUMERICAL 3-D MHD MODEL OF THE SOLAR-WIND

A fully three-dimensional, steady-state global model of the solar coro na and the solar wind is developed. A numerical, self-consistent solut ion for 3-D MHD equations is constructed for the region between the so lar photosphere and the Earth's orbit. Boundary conditions are provide d by the solar magnetic field observations. A steady-state solution is sought as a temporal relaxation to the dynamic equilibrium in the reg ion of transonic flow near the Sun and then traced to the orbit of the Earth in supersonic flow region. The unique features of the proposed model are: (a) uniform coverage and self-consistent treatment of the r egions of subsonic/sub-Alfvenic and supersonic/super-Alfvenic flows, ( b) inferring the global structure of the interplanetary medium between the solar photosphere and 1 AU based on large-scale solar magnetic fi eld data. As an experimental test for the proposed technique, photosph eric magnetic field data for CR 1682 are used to prescribe boundary co ndition near the Sun and results of a simulation are compared with spa cecraft measurements at 1 AU. The comparison demonstrates a qualitativ e agreement between computed and observed parameters. While the differ ence in densities is still significant, the 3-D model better reproduce s variations of the solar wind velocity than does the 2-D model presen ted earlier (Usmanov, 1993).