Unsolved problems in plasmasphere refilling

The plasmasphere is a cold (similar to 1eV) plasma at middle to low magnetic latitudes surrounding the Earth. Its shape is dominated by Earth's magnetic field and its cross-field motion is dominated by electric fields. It is a highly coupled part of the inner magnetosphere. Storm time conditions erode the outer plasmasphere, transporting that plasma into the dayside magnetosheath region, leaving behind a region of greatly reduced plasma density that will refill from ionospheric outflow. The processes involved in refilling remain incompletely understood. In this commentary, outstanding questions about plasmaspheric refilling are summarized in the context of recent publications.