Global MHD Modeling of the Solar Corona and Solar Wind

A. V. Usmanov and M. L. Goldstein, NASA/Goddard Space Flight Center, Greenbelt, MD 20771, USA

We present a global three-dimensional steady-state MHD model of the solar corona and solar wind that uses observations of the photospheric magnetic field in the prescription of boundary condition. As part of the boundary conditions, we also specify a flux of Alfvén waves that emanates from the Sun. The Alfvén waves provide additional acceleration for the coronal outflow in the open field regions. The waves are treated in the WKB approximation that provides a macroscopic description of the waves on the background flow and vice versa. The wave energy flux and dissipation are adjusted to generate slow and fast solar wind with the observed velocity and temperature profiles. Our simulation domain extends from the coronal base to 10 AU and consists of two regions with a computational boundary between them placed at 20 solar radii, which ensures that in the outer region the flow is both supersonic and super-Alfvénic. The inner region steady-state solution is obtained by a time-relaxation method. The solution in the outer region depends only on the values at the interface between the inner and outer regions and is constructed by forward integration along radius. The realistic magnetic field boundary conditions ensure that interaction regions between fast and slow wind form beyond about 1 AU, as observed. Furthermore, with the incorporation of wave acceleration, the Ulysses observations of both ecliptic and high latitude solar wind are recovered. Finally, we show also that the simulation results agree with the empirical model of Wang and Sheeley.