Ionospheric dynamics and drivers obtained from a physics-based data assimilation model

The ionosphere-plasmasphere system at low and middle latitudes is strongly coupled, and therefore, a study of ionospheric dynamics must take into account the interaction between the two domains. As shown by meteorologists and oceanographers, a powerful way of modeling dynamic systems is with the use of data assimilation models. At Utah State University, we have developed two data assimilation models with different complexity, and both provide global and regional specifications of the three-dimensional (3-D) ionosphere-plasmasphere densities. One of these models is a Full Physics-Based Kalman filter data assimilation model, which is based on a physics-based model for the ionosphere-plasmasphere system, a diverse array of data sources, and an ensemble Kalman filter data assimilation technique. This model covers the ionosphere-plasmasphere system from 90 to 30,000 km altitude and includes six ion species (NO⁺ N2⁺, O2⁺, O⁺, He⁺, H⁺). The strength of this model is that in addition to the global and regional 3-D ionosphere electron density distribution it also self-consistently determines the corresponding ionospheric drivers, including the thermospheric neutral winds and the low-latitude electric fields. The model can assimilate a variety of different data types, including GPS/total electron content from hundreds of ground-based receivers, in situ Ne from several DMSP satellites, bottomside Ne profiles from tens of ionosondes, and occultation data from the six COSMIC satellites. In this study, the model was used to specify the low-latitude and midlatitude ionosphere together with the ionospheric driving forces and their temporal and spatial variability.