Improvement of the IRI Model Using F-2 Layer Parameters Derived From GPS/COSMIC Radio Occulation Observations

In this study, an improved ionospheric model is presented by applying self-specified F-2 layer parameters and an adaptive topside model into the International Reference Ionosphere (IRI) model. Three F-2 layer parameters, the critical frequency (f(0)F(2)), peak height (h(m)F(2)), and the scale height (H-sc) obtained from Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) observations, are modeled by spherical harmonics expansion. The empirical orthogonal functions are used to construct the associated parameters in the adaptive topside model. The improved model is validated by incoherent scatter radar (ISR) data of Millstone station and the Global Ionospheric Maps. Results show that the NmF2 and h(m)F(2) of improved model have better agreement with ISR measurements. The vertical total electron content deviation compared with Global Ionospheric Map is discussed in different seasons and levels of solar activity. With radio occultation-based parameters, the accuracy of original IRI model is improved by 1 total electron content unit globally on average