From Stratosphere to Space: The hidden impacts of SSWs on Equatorial IT anomalies

The low-latitude Ionosphere and Thermosphere has two prominent features - the Equatorial Thermosphere Anomaly (ETA) and the Equatorial Ionization Anomaly (EIA). EIA is characterized by two plasma density crests at ~ ±15° and a dip at the magnetic equator in the F-region (e.g. Appleton, 1946; Abdu et al., 1991; Eastes et al., 2019 and Lei, 2021). ETA is present higher above in the thermosphere, with pronounced mass density trough at the dip equator and twin crests located roughly at ± 20 - 30° magnetic latitude (Mayr et al., 1974; Lei et al., 2012a and 2012b; and Lei, 2021). Despite decades of research on their formation – where fountain effects cause EIA formation and field‐aligned ion drag largely explains the formation of the ETA trough and the crests are predominantly formed via neutral-plasma collision heating (e.g. Lei et al., 2012a and 2012b; Lei, 2021) – the full spectrum of their variability remains elusive due to limited satellite observations (Wang et al., 2021). Understanding these anomalies is critical. Variations in ETA and EIA directly affect ionospheric electrodynamics and, in turn, impact satellite drag in low Earth orbit, as well as the occurrence of ionospheric scintillations that can lead to GPS disruptions (e.g. The Decadal Survey for Solar and Space Physics (Heliophysics), 2024).

Terrestrial and solar forcings greatly influence the dynamics between these anomalies. This poster focuses on one of the most dramatic lower atmospheric forcings – the sudden stratospheric warmings (SSWs). They can alter neutral wind structures from the troposphere through the ionosphere-thermosphere, affecting ETA-EIA coupling by modifying neutral-ion dynamics. Atmospheric tides propagating upward drive longitudinal structures in both anomalies, modulating their coupling. Tides from the lower atmosphere propagating to upper atmosphere can significantly drive the longitudinal structure of both anomalies, modulating the coupling between the two (e.g. Lei, 2021). This research will be the first to analyze ETA and EIA during SSW events, comparing Northern Hemisphere SSWs (e.g. 2019) with Southern Hemisphere events (e.g. 2024). Using NASA's GOLD mission and GRACE-FO satellite accelerometry data, the study will examine these phenomena across various solar flux levels under geomagnetically quiet conditions. By investigating ETA-EIA relationships during different SSW events, this research addresses critical knowledge gaps in low-latitude ion-neutral coupling, enhancing our understanding of how these dynamic atmospheric events influence equatorial ionospheric and thermospheric structures.