Plasmapause Location: Model Compared to Van Allen Probes Observations

We study the evolution of the plasmapause for a multi-year period (January 2013 to January 2017) spanning much of the Van Allen Probes mission, by comparing the output of a plasmapause test particle simulation with the spacecraft potential measured by the Electric Field and Waves (EFW) suite. Consistent with previous results, we quantify the accuracy of the model by measuring the radial difference between real and virtual satellite encounters with the plasmapause boundary. We find that model performance is better on the nightside and during active periods, and worse on the duskside/dayside and during extended quiet intervals. For two case studies, we compare the plasmapause with the locations of relativistic electron flux peaks. For global context we use the test particle plasmaspheric index Fp [Goldstein et al., 2016], the fraction of a circular drift orbit inside the plasmapause, as a proxy for the globally integrated opportunity for losses in cold plasma. We find an inverse relationship between relativistic flux and the Fp index, consistent with increased likelihood of losses in cold plasma.