A comparative case study of low-latitude ionosphere-thermosphere responses to successive wave-1-dominant and wave-2-dominant sudden stratospheric warming events in 2022 using ICON and GOLD Missions

Previous studies have demonstrated that sudden stratospheric warmings (SSWs) can have a significant impact on the Earth's ionosphere-thermosphere (IT) system. In this study, we present a case study using observations from NASA’s Ionospheric Connection Explorer (ICON) and the Global-scale Observations of the Limb and Disk (GOLD) mission to examine low-latitude IT responses during two successive SSW events in 2022 with different wavenumbers of the dominant planetary waves (wave-1 and wave-2), and we compare their event-time responses relative to the same pre-SSW reference period. Compared with observations during pre-SSW periods, the first SSW event is characterized by southeastward wind accelerations below ~99 km and northwestward wind accelerations above ~99 km within the latitude range of 0°–40°N. In contrast, the second SSW event exhibits westward and northward acceleration (below ~99 km) and eastward and southward acceleration at higher altitudes (above ~99 km). Equatorial E×B vertical ion drifts show upward in the morning during the first SSW and downward perturbations in the postmidnight hours during the second, which may be attributed to changes in zonal winds. Meanwhile, significant enhancement of O/N2 (the column density ratio of atomic oxygen to molecular nitrogen) is observed during the daytime, along with a rise of approximately 46 K in thermospheric temperature at the altitude of 150 km during the first SSW event. The O/N2 and thermospheric temperature increase also during the second. The net effects of electric fields and atmospheric circulation result in nighttime F-region electron density during the first SSW event and a decrease during the second, as observed by GOLD. During the second SSW, the semidiurnal migrating tide (SW2) is enhanced in the low-latitude region.