Specification of the Earth\'s Plasmasphere with Data Assimilation

This document describes initial work on using data assimilation to model the Earth's plasmasphere. The researchers used an ensemble data assimilation approach inspired by Ensemble Kalman filtering with the Ober et al plasmasphere model. They conducted simulations using real KP index values from December 2006 to generate simulated satellite density measurements. The data assimilation scheme was able to accurately reproduce the overall plasmasphere structure during quiet periods but performed poorly during active periods, tending to place the plasmapause closer to Earth than in the input model. Using more ensemble members and all available satellite data improved the results.