Providing global neutral density estimates using the CTIPe model and data assimilation

Accurate estimation of thermospheric neutral density is vital for atmospheric drag compensation. Actual measurements of thermospheric neutral density are rare, and often limited to specific altitude ranges. Numerical models are often used as a substitute, sometimes in conjunction with data assimilation schemes.

During geomagnetic storms, having an accurate representation of the thermosphere-ionosphere (TI) is vital, since climatological models cannot accurately reproduce the system response. Recently, the physics-based Coupled Thermosphere Ionosphere Plasmasphere electrodynamics (CTIPe) model has been shown to provide accurate global estimates of neutral density when used in conjunction with the Thermosphere Ionosphere Data Assimilation scheme (TIDA).

This approach adds the model inputs to the state vector and better accounts for the strongly forced nature of the TI. In this study, we expand on previous work by demonstrating the use of TIDA-CTIPe for neutral density estimation over a much broader time interval, covering multiple geomagnetic events.

We demonstrate the capability to improve global estimates of neutral density by assimilating measurements in a narrow altitude range, from the CHAMP, GRACE and SWARM missions. Additionally, we demonstrate TIDA's capability to improve the thermospheric neutral density by assimilating different data types, such as COSMIC-2 derived TEC. Finally, we discuss the need for near-real-time data for potential forecasting applications.