Ionospheric electron density characteristics over Africa from FORMOSAT-3/COSMIC radio occultation

With the widespread availability of ground and space-based global navigation satellite system (GNSS) observables, continuous and long-term explorations of ionospheric variations have been made possible worldwide or on regional basis with improved accuracy. The Formosa Satellite Mission#3/Constellation Observing System for Meteorology, Ionosphere, and Climate (FORMOSAT-3/COSMIC) mission has a huge database of radio occultation (RO) soundings at regional and global scales with a high vertical resolution. Comparative studies between radio occultation, incoherent scatter radar and ionosonde observations indicate that COSMIC profiles agree well with ground measurements. The present paper investigates the ionospheric profiles over Africa using COSMIC data for the period from 2006 to 2017, representing almost a solar cycle year of study. The spatiotemporal variation of electron density confirms a hemispheric asymmetry among the equinoctial seasons and the solstice seasons during both low and moderate solar activity. Seasonal/winter anomaly manifestation is also clearly noticed in our observations with relatively high electron density during the winter solstice than the summer solstice. Moreover, the electron density over the region show apparent spatial and temporal variations identical to earlier ground-based ionospheric monitoring results over the African region. The outcomes from this study would strengthen the understanding of the ionospheric alterations and modelling activities in Africa, especially the areas with inadequate ground-based measuring instruments, hence, our results may complement the progress in global ionospheric modelling.