Equatorial Ionization Anomaly Crest Parameters Modeling

 Knowing the locations of the north and south Equatorial Ionization Anomaly (EIA) crests and their corresponding widths is essential for characterizing the spatiotemporal and solar activity variations of the low latitude ionosphere. The crest region is characterized by strong electron density gradients that significantly affect GNSS applications. However, there is still a lack of complete characterization and modeling of the spatiotemporal and solar activity variations of the EIA crest positions and widths. Therefore, the purpose of this study is to characterize and model the spatiotemporal and solar activity variations of EIA crest widths and positions. These characteristics are described and modeled using 13 years (2009-2017 and 2020-2023) NmF2 data, which are obtained from radio occultation electron density profiles of GRACE, COSMIC-1, and COSMIC-2 satellites over the globe. Crest positions and widths exhibit diurnal, semi-diurnal, and annual variations. There is a slight linear correlation between the solar activity and the crest positions and widths. Furthermore, longitudinal variations in the geomagnetic field declination and the interplay between wave number 3 diurnal tides and planetary waves may be related to longitudinal variations in the crest positions and widths. The results of the analysis are used to create semi-empirical EIA crest position and width models. These models provide a good description of the crest widths and positions verified by vTEC altimeter measurements. These models can serve as subroutines for the improvement of current ionospheric TEC and F2-layer maximum electron density models, applicable for improving terrestrial communications and GNSS positioning and navigation.