A Magnetohydrodynamic Test of the Wang-Sheeley Model

The Wang-Sheeley empirical model relates the solar wind speed observed at the Earth with the divergence rate of magnetic flux tubes expanding in the solar corona. This model is based on a statistically significant correlation between an open flux tube divergence parameter "fs" derived from photospheric field synoptic maps, and satellite observations of the solar wind speed. They found that the fast solar wind emanates from regions of small magnetic divergence, while slow solar wind comes from regions of high magnetic divergence. Arge and Pizzo (2000) have since improved the reliability of the Wang-Sheeley model by including an empirical function that relates the magnetic expansion factor to the solar wind speed at the source surface, and a scheme to account for stream interactions as the solar wind propagates outward. We use a three-dimensional MHD model of the solar corona to empirically test the Wang-Sheely model and the improvements made by Arge and Pizzo. These results may provide insight into what additional heating may be necessary in different flux tube geometries in order to obtain to the observed relationship with solar