Density Gradients at and Near the Plasmapause

We explore density gradients observed at and near the plasmapause using spacecraft potential data from the EFI instruments on the five THEMIS spacecraft. The plasmasphere boundary is an important region in the inner magnetosphere for wave growth, decay, and propagation. Through waves which occur there, low energy particles couple to the highest energy particles thereby connecting the entire particle population in inner magnetosphere. We present here statistics on the structure, size, location, and occurrence of plasma density gradients and their relation to geomagnetic activity. The THEMIS mission and its five spacecraft in orbits of different periods present an idea platform to study the plasmasphere boundary region, providing different local time traversals with a variety of revisit times needed to separate spatial and temporal structure.