Regional ionospheric total electron content over Africa from ground-based GNSS observations

Due to the wide use of GNSS receivers both on satellites at low earth orbit and on the ground, continuous and long-time ionospheric data with increasing accuracy have been obtained and used to study variations in the Earth’s ionosphere. Daily data from 2010.001 to 2017.365 sampled at 30 seconds from 104 African Geodetic Reference Frame (AFREF) dual-frequency GNSS Continuously Operating Reference Stations receivers distributed across Africa, were used in this study. Single Layer Model which assumes that all free electrons are concentrated in a shell of infinitesimal thickness, provides determining ionospheric total electron content value. In this study, the SLM model was used to derive total electron content values. TEC values obtained from the AFREF GNSS CORS measurements were compared with the TEC values from the global ionosphere maps provided by the Centre for Orbit Determination in Europe (CODE). The comparison was achieved by means of time series and wavelet analyses, and also by considering various model validation metrics. Comparative results for TEC estimates from both datasets based on goodness of fit measures, time series and wavelet analyses show good agreement on a statistical basis (r = 0.948) within the limits of experimental observation.