Development of the E-region Prompt Radio Occultation Based Electron Density (E-PROBED) Model: Progress on the Background Ionosphere Component

The E-region (80–140 km) ionosphere plays an important role in operational systems reliant on radio wave trans-ionospheric propagation because of its absorption of short-wave signals (e.g., high-frequency, HF radio) and reflection of long-wave communication and navigation radios (e.g., very low frequency, or VLF). It is a critical interface between Earth’s atmosphere and ionosphere and is associated with large variability from dynamically, chemically, radiatively and electrically coupled processes. Yet, a reliable E-region electron density (Ne) model is still lacking, especially for global operations because of the lack of global-scale observations. Most of our E-region observations are from incoherent scatter radars and ionosondes. To address these scientific and operational issues, this work aims to develop the E-Region Prompt Radio Occultation Based Electron Density Model (E-PROBED Model), a quick-run empirical global E-region operational model built using multi-satellite and multi-decade global observations of E-region electron density profiles recently retrieved from GNSS Radio Occultation (GNSS RO) measurements. For this presentation, we share progress on the development of the E-PROBED Model’s background ionosphere component. Once the background ionosphere component is developed, we will proceed with the development of the geomagnetic storm-time component. To construct the model’s background ionosphere component, we first took the GNSS RO profiles and binned them into monthly-mean latitude-local time-altitude bins. All results in the presentation solely used COSMIC-1 electron density profiles. Then, the altitude profile on each longitude-latitude local time bin is fitted into a chapman function. The fit involves varying only two parameters called NmE and HmE. This would then give us multi-year latitude-local time profiles of both parameters. We then construct empirical relationships between these parameters and the solar zenith angle, select solar indices and select geomagnetic indices. This presentation will show a preliminary version of the model that already captures the general local-time and seasonal variabilities of E-region electron density as observed by COSMIC-1.