Coronal magnetic field topology and source of fast solar wind

We have developed a steady state, 2D semiempirical MHD model of the solar c orona and the solar wind with many surprising results. This model for the f irst time shows, that the boundary between the fast and the slow solar wind as observed by Ulysses beyond 1 AU, is established in the low corona. The fastest wind observed by Ulysses (680-780 km/s) originates from the polar c oronal holes at 70 degrees-90 degrees latitude at the Sun. Rapidly divergin g magnetic field geometry accounts for the fast wind reaching down to a lat itude of +/-30 degrees at the orbit of Earth. The gradual increase in the f ast wind observed by Ulysses, with latitude, can be explained by an increas ing field strength towards the poles, which causes Alfven wave energy flux to increase towards the poles. Empirically there is a direct relationship b etween this gradual increase in wind speed and the expansion factor, f, com puted at r > 20 R.. This relationship is inverse if f is computed very clos e to the Sun.