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° ？？？？ × 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.