2.3 ExB drifts

The magnetospheric potential is mapped onto SAMI3’s magnetic apex coordinates and superposed with the internal wind-driven dynamo. The spatial derivative of this combined potential is calculated to find the electric field E . The electric field producesE xB ion drifts in the model, resulting in predictions of largely photo-ionized F-region plasma flowing into the polar cap from the dayside.

3. Results

Over the course of the experiment, the most intense period of disturbances occurred in the later hours of 23 May 2014, between 19 – 22 UT. Relevant DMSP passes during this period were identified and used to assess the accuracy of the AMPERE-derived potentials. The flagged “good” data from UT Dallas were decimated and mapped to a geographic reference frame before plotting. Results of three passes (two from F16 and one from F18, spaced by ~2 hours total) are shown in Figure 4, with the pass times indicated in each subplot. Note that these (and subsequent) plots are in geographic coordinates and so the subsolar point is in the bottom-left. The potentials closest to the center of each pass are shown. In these cases there was no great variation between timesteps across each pass, and the three cases are broadly consistent with each other. In all cases, DMSP velocities and AMPERE-derived potentials show close agreement in the evening cell (negative potential), where the velocity turning points match the location of the minimum potential, and the velocities line up well to the potential contours. However there are some discrepancies in the morning cell (shown in blue), where the DMSP data do not show the turning points that would be expected from the modeled potential.