GOLD Synoptic Observations of Quasi‐6‐Day Wave Modulations of Post‐Sunset Equatorial Ionization Anomaly During the September 2019 Antarctic Sudden Stratospheric Warming

Abstract Using observations from the Global‐scale Observations of the Limb and Disk (GOLD) mission, we investigate post‐sunset ionospheric responses to the September 2019 Antarctic sudden stratospheric warming –first ever from a synoptic perspective. Observations reveal a prevalent quasi‐6‐day periodicity in the equatorial ionization anomaly region over South America and the Atlantic, coincident with enhanced quasi‐6‐day wave (Q6DW) activity in the mesosphere (Liu et al., 2021, https://doi.org/10.1029/2020JA028909 ). The atmosphere‐ionosphere coupling via large‐scale waves is rarely studied over the ocean due to the lack of observations. More importantly, further analyses suggest that multiple pathways are involved in transmitting the quasi‐6‐day periodicity from the middle atmosphere into the post‐sunset F‐region ionosphere, including modulation of F‐region field aligned winds and pre‐reversal enhancements by the tides and or Q6DW. A remarkable depletion in electron density, attributable to the overall change in thermosphere composition driven by the dissipative tides and or Q6DWs, is also seen during the period of enhanced Q6DW activity.