Characterization and Modeling of Equatorial Ionization Anomaly Crest and Trough Positions Using Multiple-Source Fused Data During the Solar Minimum Period

Abstract

Characterizing the spatial and temporal variations of the equatorial ionization anomaly (EIA) is essential for understanding ionospheric dynamical processes and further developing empirical total electron content (TEC) models. Using the multiple-source fused TEC data during the solar minimum period, the EIA crest and trough positions were extracted, analyzed, and modeled. We primarily investigated the longitudinal differences in the probability of bimodal occurrence (PBO) and its time dependence at each longitude. The main results are as follows: (a) The PBO exhibits significant longitudinal variation, with a wave-number-3 structure from 11:00 to 13:00 LT and a wave-number-4 structure around 15:00 LT. There is a sequential enhancement and recession among four sectors from east to west between 09:00 LT and 15:00 LT. (b) The seasonal dependence of PBO varies across sectors, particularly during the solstice months. The wavenumber spectral components of TEC along the longitudinal direction exhibit similar temporal patterns, suggesting that the atmospheric tides may modulate the local time and seasonal dependence of PBO. (c) Two EIA position models were developed. The model based on longitude and month can accurately capture the seasonal and spatial variations in the locations of peaks and troughs, with a mean residual of 0° and a standard deviation of 2.1°–2.3°.