Development of the Ionospheric E-Region Prompt Radio Occultation Based Electron Density (E-PROBED) Model

This work reports the development of the first version of the E-region Prompt Radio Occultation Based Electron Density (E-PROBED) Model. This is an empirical model of E-region electron density (Ne) between 90 and 120 km developed using radio occultation measurements from the COSMIC-1 mission. This first version captures more than 80% of the observed variability in monthly-mean latitude-local time-altitude E-region Ne profiles but it does not account for longitudinal variability at constant local-time. This work also reports a validation of E-PROBED simulations through comparisons with ionosondes and incoherent scatter radar (ISR) E-region Ne profiles. E-PROBED generally agrees with these ground-based observations during day-time. During night-time, there is a large disparity between E-PROBED and ISR values. Finally, this work compares E-PROBED with E-region Ne simulated by the International Reference Ionosphere (IRI) and the Specified Dynamics—Whole Atmosphere Community Climate Model with Ionosphere/Thermosphere eXtension (SD-WACCM-X). One of the main differences amongst these models is on the simulation of variabilities that cannot be attributed to photoionization. IRI barely simulates any variability not driven by photoionization. Both E-PROBED and SD-WACCM-X simulates variability not driven by photoionization. Another main difference is in the absolute magnitude of night-time E-region Ne values. Both IRI and SD-WACCM-X are substantially lower than E-PROBED. This work first concludes that E-PROBED can conveniently provide E-region Ne latitude—local time variabilities and structures that COSMIC-1 observes. This work also concludes that E-region Ne have significant non-photoionization driven variabilities.