Testing the Hill model of transpolar potential with Super Dual Auroral Radar Network observations

[1] We use a data set consisting of periods for which the transpolar ionospheric potential ( pc) is well-determined by Super Dual Auroral Radar Network (SuperDARN) data to test the Hill model. The Hill model, as formulated by Siscoe et al. [2002], specifies pc as a function of solar wind speed and ram pressure, the interplanetary magnetic field, the reconnection electric field (Er), and the ionospheric conductance ( ). The periods used in our study were identified as times when the interplanetary electric field was quasi-stable for and SuperDARN coverage was sufficient to determine pc. SuperDARN-determined pc ( pc ) is compared to pc determined using the Hill model ( pc ) for 1317 10-min periods. A minimum in the root-meansquare difference between ( pc ) (Er) and ( pc ) (Er) is achieved when = 23 S and a constant potential, 0 = 17 kV, are used. Some aspects of the data agree very well for these values of and 0, including the mean value of pc(Er) and that both data sets clearly indicate saturation at higher values of Er. The ram pressure dependence of ( pc ), however, is inconsistent with that of ( pc ) and suggests that should be lower than 23 S. There is also significantly more variability in ( pc ) for all values of Er than the Hill model predicts.