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

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 x B drift, and enhanced the Equatorial Ionization Anomaly (EIA) during the first main phase. (b) The EIA asymmetry in the region east of 70 degrees 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 degrees, corresponding to a rare Apex altitude of similar to 2,600 km at magnetic equator. (d) On 24 April, the thermospheric composition disturbances with high Sigma O/N-2 were concentrated in the southern hemisphere, and resulted in the positive storm over South America.