Longitudinal, Latitudinal, and Local Time Variations of the 14.5‐Day Periodic Oscillation in the Ionosphere During 2014–2015 SSW

Abstract

Based on global total electron content (TEC) maps from the International Global Navigation Satellite Systems Service (IGS), the ionospheric perturbations during the 2014–2015 sudden stratospheric warming (SSW) event were investigated. The analyses revealed both phase‐shifted semidiurnal perturbations and 14.5‐day periodic signal with zonal wavenumber 0 in the IGS TEC, indicating an enhanced lunar tidal impact on the ionosphere during the 2014–2015 SSW period. The 14.5‐day periodic oscillation in the IGS TEC presents an obvious latitudinal variation, with the maximum appearing in Equatorial Ionization Anomaly crest regions, which is due to the modulation of the equatorial ionospheric fountain effect by wind perturbations modulated by the lunar tide. Additionally, the 14.5‐day periodic oscillation presents a longitudinal pattern with three peaks in the northern hemisphere and four peaks in the southern hemisphere. Local time dependence of the 14.5‐day periodic perturbation is also significant.