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 the ICON and GOLD missions

Previous studies have demonstrated that sudden stratospheric warming (SSW) events can have a substantial impact on the Earth’s ionosphere–thermosphere (IT) system. In this study, we present a case study using observations from that National Aeronautics and Space Administration’s (NASA’s) Ionospheric Connection Explorer (ICON) and Global-scale Observations of the Limb and Disk (GOLD) missions 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 the 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\times B vertical ion drifts show upward drift in the morning during the first SSW and downward perturbations in the post midnight hours during the second, which may be attributed to changes in zonal winds. Meanwhile, significant enhancement of ΣO/N₂ (the column density ratio of atomic oxygen to molecular nitrogen) is observed during the daytime, along with a rise of ~46 K in thermospheric temperature at an altitude of 150 km during the first SSW event. The ΣO/N₂ and thermospheric temperature also increase during the second. The net effects of electric fields and atmospheric circulation result in an increase 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 event, the semidiurnal migrating tide (SW2) is enhanced in the low-latitude region.