A new global TEC empirical model based on fusing multi-source data

The global TEC empirical model established with the TEC grid data of IGS as the background has poor prediction accuracy in marine areas, and its ability to describe some ionospheric anomalies is insufficient. In response to the above two problems, we use spherical harmonic (SH) to fuse multi-source TEC data as a modeling dataset and evaluate the accuracy of the fused products. When modeling, we consider three ionospheric anomalies, namely mid-latitude summer nighttime anomaly (MSNA), equatorial ionization anomaly (EIA), and “hysteresis effect,” and establish corresponding model components. We apply the nonlinear least-squares method to establish a global ionospheric TEC empirical model called the TEC model of multi-source fusion (TECM-MF) and verify the model. Results show that: (i) fusion products are valid and reliable modeling data for building global TEC model. (ii) The TECM-MF fits the Fusion TEC input data with a zero bias and a RMS of 3.9 TECU. The model can better show the diurnal, seasonal, and annual variations of the fusion dataset and the “hysteresis effect” of TEC. (iii) In the MSNA area, the prediction ability of the TECM-MF is better, the standard deviation is lower than that of NTCM-GL and Nequick2, close to 1 TECU, and the accuracy is consistent with IRI2016.