Algorithm and Product Generation of a Global Ionospheric Tomography Model Based on Multisource Data

Three-dimensional ionospheric tomography is an essential method for understanding spatial variations in electron density and for providing physical interpretations of anomaly evolution. Global ionospheric tomography enables more comprehensive analysis of electron content variations across different altitudinal layers and the propagation of ionospheric disturbances. This study utilizes observational data from Global Navigation Satellite System (GNSS), FORMOSAT-7/COSMIC-2 (COSMIC-2), and JASON-3, in conjunction with the International Reference Ionosphere (IRI-2020) model and global ionospheric map (GIM) from the Center for Orbit Determination in Europe (CODE-GIM) data to develop a function-based global tomography model [functional-based global computerized ionospheric tomography (F-GCIT)]. The results of this model are continuously disseminated in ionosphere map exchange (IONEX) format. The F-GCIT model is divided into four layers: 0–250, 250–350, 350–550, and above 550 km, with each layer represented using spherical harmonics (SHs), covering latitudes from 40°S to 40°N and longitudes from 180°W to 180°E, with a temporal resolution of 1 h. Using product data spanning from October 2021 to October 2023, using CODE-GIM, ionosonde, IRI-2020, COSMIC-2, and incoherent scattering sounding data as references, we analyzed the accuracy of the F-GCIT model. Compared to the regional pixel-based computerized ionospheric tomography, F-GCIT demonstrates closer agreement with ISR profiles.