SEMIEMPIRICAL TWO-DIMENSIONAL MAGNETOHYDRODYNAMIC MODEL OF THE SOLAR CORONA AND INTERPLANETARY MEDIUM

摘要

We have developed a two-dimensional semiempirical MHD model of the solar corona and solar wind. The model uses empirically derived electron density profiles from white-light coronagraph data measured during the Skylab period and an empirically derived model of the magnetic field which is fitted to observed streamer topologies, which also come from the white-light coronagraph data. The electron density model comes from that developed by Guhathakurta and coworkers. The electron density model is extended into interplanetary space by using electron densities derived from the Ulysses plasma instru- ment. The model also requires an estimate of the solar wind velocity as a function of heliographic lati- tude and radial component of the magnetic field at I AU, both of which can be provided by the Ulysses spacecraft. The model makes estimates as a function of radial distance and latitude of various fluid parameters of the plasma such as flow velocity V, effective temperature T_eff,and effective heat flux q_eff, which are derived from the equations of conservation of mass, momentum, and energy, respectively. The term "effective" indicates that wave contributions could be present. The model naturally provides the spiral pattern of the magnetic field far from the Sun and an estimate of the large-scale surface magnetic field at the Sun, which we estimate to be approx 12-15 G. The magnetic field model shows that the large-scale surface magnetic field is dominated by an octupole term. The model is a steady state calculation which makes the assumption of azimuthal symmetry and solves the v