Characteristics of Global EIA in Moderate-to-High Solar Activity Years by Swarm Satellites Data

Although the equatorial ionization anomaly (EIA) has been widely studied, there is little research on the global longitudinal and seasonal variations of EIA Occurrence Rate (EOR) at different altitude during different local times in moderate-to-high solar activity years. In this study, EOR has been investigated by electron density data from Swarm satellites during the moderate-to-high solar activity years of 2022-2023 under quiet magnetic conditions. Longitudinal distributions of EOR at Swarm-A/C and Swarm-B satellite altitudes (~462km and ~510km) during different local time (LT) sectors and seasons were analyzed. Key findings include: (1) EOR values at Swarm-A/C satellite altitude are generally higher than those at Swarm-B altitude, with a more pronounced EOR difference between the two altitudes during 18-22LT compared to 09-18LT. (2) During 09-22LT, EOR values generally exhibit maxima in equinoxes and minima in summer. (3) During 13-18LT, EOR displays a three-peak longitudinal structure in winter, whereas four-peak structures emerge in equinoxes and summer. During 18-22LT, EOR peaks at -50°E in winter, while EOR shows small longitudinal fluctuations in equinoxes, and exhibits maximum values near -160°E and 5°E in summer.