The ionosphere electron density spatio-temporal modeling based on the Slepian basis functions

Abstract

Radio occultation (RO) is one of the most novel satellite approaches that can be used to study ionospheric electron densities, by combining the observations of global navigation satellite systems and low earth orbiting (LEO) satellites to determine ionospheric electron density profiles with high vertical resolutions. This study aims at developing a multi-dimensional model of the electron density derived from ionospheric GPS RO measurements by the FORMOSAT-3/COSMIC satellites. In order to develop a 4D local model for the electron density, a Slepian function was used to account for longitudinal and latitudinal variations, the B-spline was utilized for time variations and the Chapman profile function was used to express the height variations of the electron density, in this way the parameters of the Chapman function, namely the maximum electron density of the F2 layer (NmF2) and the corresponding F2 peak height (hmF2) were modeled. The coefficients of the two sets of the Slepian functions were estimated using the least-squares adjustment technique. In order to validate the accuracy of the proposed technique, two approaches are considered: (1) The estimated F2-peak values were compared with the IRI model and ionosonde stations values, (2) Comparing the modeled electron density profile against the one estimated using RO methods.