Neutral Atmosphere Data Assimilation to Investigate Storm-Time Ionospheric Driving in WAM-IPE

The thermosphere-ionosphere system is strongly modulated by solar EUV and geomagnetic variability. This external forcing influences the ionosphere by driving electrodynamic processes and photoionization (direct forcing) and by driving circulation, composition, and heating processes in the neutral atmosphere that impact the plasma through thermosphere-ionosphere coupling (indirect forcing). The Iterative Driver Estimation and Assimilation (IDEA) data assimilation scheme has been implemented in the global, coupled NOAA/NWS Whole Atmosphere Model-Ionosphere Plasmasphere Electrodynamics (WAM-IPE) model to ingest neutral mass density observations in order to provide corrections to the input solar and geomagnetic drivers. We test WAM-IPE with different data assimilation and driver configurations to investigate the relative importance of the direct and indirect forcing of the ionosphere within WAM-IPE for the 2013 St. Patrick's Day geomagnetic storm. The driving mechanisms, along with the coupling between the thermosphere and ionosphere, are evaluated through comparison of each model configuration with the CEDAR Madrigal database total electron content (TEC) maps.