Low-Latitude Ionospheric Responses to the Severe Geomagnetic Storm During 23–25 April 2023 Over the American Sector

Abstract

The impacts of the severe geomagnetic storm on 23–25 April 2023 on the low-latitude ionosphere over the American sector are investigated. Based on the ground-based and spaceborne instruments, a series of storm-associated ionospheric disturbances have been observed as follows: (a) The eastward Prompt Penetration Electric Fields intensified the equatorial upward E × B drift, and enhanced the Equatorial Ionization Anomaly (EIA) during the first main phase. (b) The EIA asymmetry in the region east of 70°W and one-sided F3 layer in the northern hemisphere are observed and are attributed to the strong southward transequatorial winds. (c) The disturbances of electric field and neutral winds raised the low-latitude and equatorial F-layer dramatically, and generated post-midnight Equatorial Plasma Bubbles. These bubbles rapidly extended to the magnetic latitude of 30°, corresponding to a rare Apex altitude of ∼2,600 km at magnetic equator. (d) On 24 April, the thermospheric composition disturbances with high ΣO/N₂ were concentrated in the southern hemisphere, and resulted in the positive storm over South America.