CNES real-time ionospheric product accuracy analysis based on empirical orthogonal function decomposition

Total electron content (TEC) is a key parameter in the mitigation of ionospheric effects on radio systems. This paper studied the performances of ionospheric TEC obtained from Centre National d'Etudes Spatiales (CNES) real-time ionospheric products. Taking the international global navigation satellite system service (IGS) global ionospheric map (GIM) as a reference, the deviation and root mean square of the TEC estimated by the CNES real-time TEC and NeQuick-G model were compared. Results showed that the CNES real-time ionospheric TEC and IGS GIM describe the global ionospheric temporal and spatial changes more closely. By using the empirical orthogonal function (EOF), the temporal and spatial characteristics of CNES real-time TEC and GIM TEC from day of year 230 to day of year 259 in 2021 were extracted and compared. The following main spatial variation patterns were extracted: the changes in geomagnetic latitude reflecting daily mean solar forcing and the changes in diurnal and semi-diurnal cycles. The time-varying characteristics of CNES real-time TEC and GIM TEC were compared by extracting the same EOF basis functions E-1-E-5. The EOF decomposition coefficients A(1) - A(5) reflect the strength of the spatial variation patterns, and they are all strongly correlated with solar activity. Among them, the intensity of diurnal cycle variations contained in CNES real-time TEC is in good agreement with GIM TEC, but the intensities of changes in geomagnetic latitude and semi-diurnal cycles are weaker than those of GIM TEC.