3-D Regional Imaging of Ionosphere Over Africa Through Assimilating Satellite and Ground-Based Data

Abstract

In this study, the first high-resolution regional ionospheric model over Africa and adjacent areas (−40–40°N latitude, 30°W–60°E longitude, and 80–1,400 km in altitude) is constructed by assimilating ground-based slant total electron content (STEC) from 40 GPS (Global Positioning System) receiver stations and space-based NmF2 (ionospheric F2 peak density) data from C2 (Constellation Observing System for Meteorology, Ionosphere, and Climate-2) into the International Reference Ionosphere (IRI-2016) model. An Ionospheric Data Assimilation Four-Dimensional (IDA4D) technique was used to estimate electron densities as high as 1.5° (Formula presented.) 3° in latitude and longitude, 10 km in altitude in the E and F regions, and 15 min in universal time. Two experiments were run for the following data sets: (a) GPS-STECs only and (b) GPS-STECs and NmF2s from C2 during geomagnetically quiet (6–11 May 2021) and storm periods (12–14 May 2021). The IDA4D assimilation results are validated using independent C2 control group, ionosonde, and JASON-3 observations. Results for the storm period show that experiment 2 reduces the average root-mean-square error (RMSE) of NmF2, foF2, and VTEC by 34%, 31%, and 34%, respectively, and increases the associated correlations by 10%, 14%, and 2% over IRI, respectively. Using IDA4D, we observed enhancement of the northern crest equatorial ionization anomaly in the late evening that was caused by upward and northward plasma transport.