Statistical Study of Magnetopause Boundary Region Vortices Observed During Modeled Solar Wind Conditions

With MHD simulations using fixed solar wind speeds and a step function in IMF direction we have found vortices on the magnetopause flanks near the ecliptic plane. We compare and contrast a case of nominal solar wind speed, around 360 km/s, and a higher solar wind speed, 700 km/s, both starting with southward IMF, -5 nT, for 15 minutes, and then turning northward, +5 nT for two hours. A total of 11 vortices were found for the case with nominal solar wind speed. Most of these vortices evolved into more complex or more defined vortices during their one-hour duration. They exhibited peculiar characteristics; their rotation axis were primarily in the x or y direction even though the IMF was predominantly in the z direction. Most of them were large in scale (6-10 RE) and also appeared to have a symmetry in which dawn and dusk vortices would develop simultaneously on the magnetopause flanks with the same rotation direction. Curiously, vortices would also develop simultaneously at the same x-y location but with a different z coordinate, and these would always rotate in the opposite sense to those in the ecliptic plane, i.e, ones at z=0 rotated clockwise and ones at z=-8 rotated counterclockwise. For the case with higher solar wind speed, 700 km/s, around 25 vortices were found exhibiting the same characteristics, but with longer durations. In a previous study we presented a total of 304 vortices found near the ecliptic plane on the magnetopause flanks using simulated MHD data driven by real solar wind conditions. Comparison of these results to our recent simulations with fixed conditions will also be presented.