Importance of global magnetic field geometry and density distribution in solar wind modeling

Abstract

We have developed a 2D semi-empirical MHD model (1) of the solar corona and the solar wind. The model uses empirically derived electron density profiles from the white light coronagraph data measured during the Whole Sun Month observing campaign of SOHO and an empirically derived model of the magnetic field which is fit to observed coronal hole boundary which come from white light and EUV observations. The electron density model is extended into interplanetary space by using electron densities derived from the Ulysses instrument. The model also requires an estimate of the solar wind velocity as a function of heliographic latitude and the 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 fluid parameters of the plasma such as flow velocity V⃗, temperature Teff, and heat flux qeff which are derived from the equations of conservations of mass, momentum and energy, respectively in the rotating frame of the Sun. The term effective indicates possible wave contributions. Both the observations as well as the model results of the various plasma properties show a clear separation at the boundary of the fast and slow solar wind. This boundary is directly established by the global magnetic field topology inferred from observations.