Characterization and Climatological Modeling of Equatorial Ionization Anomaly (EIA) Crest Position

Abstract

The Equatorial Ionization Anomaly (EIA) is characterized by strong ionospheric gradients that complicate ionospheric modeling and mitigation of ionospheric impact on Global Navigation Satellite System applications. In this study, the variation of EIA crest locations as a function of longitude and solar radio flux index F10.7 has been derived and modeled. Seven years (2013–2019) of ionospheric NmF2 and insitu ion density data from Constellation Observing System for Meteorology Ionosphere and Climate and Swarm-A satellites have been used. We find that the distance between the northern and southern crest of EIA grows slightly with increase of solar flux. The position of the crests of EIA follows a wave number 4 structure with peak values at around −130°, 0°, and 100°E. At the altitude of Swarm-A (about 460 km), the equatorial crests are found closer to the geomagnetic dip equator than they are at the peak density height hmF2 (about 310 km) which may be due to the spatial variations of geomagnetic field strength. Accordingly, two Crest Position climatological Models have been developed, one for the F2 Peak height (CPM-F2P) and the other one for Swarm-A height (CPM-SAH).