Semiempirical two-dimensional magnetohydrodynamic model of the solar corona and interplanetary medium

We have developed a two-dimensional semiempirical MHD model of the solar co rona and solar wind. The model uses empirically derived electron density pr ofiles from white-light coronagraph data measured during the Skylab period and an empirically derived model of the magnetic field which is fitted to o bserved streamer topologies, which also come from the white-light coronagra ph data. The electron density model comes from that developed by Guhathakur ta and coworkers. The electron density model is extended into interplanetar y space by using electron densities derived from the Ulysses plasma instrum ent. The model also requires an estimate of the solar wind velocity as a fu nction of heliographic latitude and radial component of the magnetic field at 1 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 f luid parameters of the plasma such as flow velocity V, effective temperatur e T-eff, and effective heat flux q(eff), which are derived from the equatio ns of conservation of mass, momentum, and energy, respectively. The term "e ffective" indicates that wave contributions could be present. The model nat urally provides the spiral pattern of the magnetic field far from the Sun a nd an estimate of the large-scale surface magnetic field at the Sun, which we estimate to be similar to 12-15 G. The magnetic field model shows that t he large-scale surface magnetic held is dominated by an octupole term. The model is a steady state calculation which makes the assumption of azimuthal symmetry and solves the various conservation equations in the rotating fra me of the Sun. The conservation equations are integrated along the magnetic field direction in the rotating frame of the Sun, thus providing a nearly self-consistent calculation of the fluid parameters. The model makes a mini mum number of assumptions about the physics of the solar corona and solar w ind and should provide a very accurate empirical description of the solar c orona and solar wind. Once estimates of mass density rho, flow velocity V, effective temperature T-eff, effective heat flux q(eff), and magnetic field B are computed from the model and waves are assumed unimportant, all other plasma parameters such as Mach number, Alfven speed, gyrofrequency, etc. c an be derived as a function of radial distance and latitude from the Sun. T he model can be used as a planning tool for such missions as Solar Probe an d provide an empirical framework for theoretical models of the solar corona and solar wind. The model will be used to construct a semiempirical MHD de scription of the steady state solar corona and solar wind using the SOHO La rge Angle Spectrometric Coronagraph (LASCO) polarized brightness white-ligh t coronagraph data, SOHO Extreme Ultraviolet Imaging Telescope data, and Ul ysses plasma data.