Shown above is the most recent run of the Coronal Mass Ejection (CME) or “storm” version of the Wang-Sheely-Arge (WSA)-Enlil model of the solar wind. While the sun constantly emanates an outward wind referred to as the solar wind (seen in the ‘Ambient’ model), at irregular intervals major eruptions originating at the Sun are propelled out with the solar wind. Variations in the density and speed in these storms is much more dramatic than on a “fair-weather” day. Knowing when these wind and density structures will arrive in advance is important because they produce geomagnetic storms and can pump up the Earth’s radiation belts, creating problems for satellites. While the storm model is useful, even during fair-weather days there is something interesting happening.
The top plots shows solar wind density and the bottom plots show solar wind velocity. The circles on the left are a view from above the North Pole of the Sun and Earth, as if you are looking down from above. The Sun is the yellow dot in the center and the Earth is the green dot on the right. Also shown are the locations of the two STEREO satellites. The ‘wedges’ in the center are essentially a side view, with north at the top and south at the bottom. The graphs on the right show the model predictions for density and velocity at the specific locations of Earth and the two STEREO spacecraft. The yellow vertical line is in sync with the movies on the left, so you can see how the values of density and velocity correspond to particular solar wind structures.