Rapid Reversal of Hemispheric Asymmetry in the Intensity of EIA Crests During the Geomagnetic Storm of 23 April 2023: A Unique Observation From GOLD

Abstract This study, using the peak electron density of Ionospheric F‐region from the Global‐scale Observations of the Limb and Disk reports, for the first time, a unique phenomenon: the rapid reversal of the intensity of the Equatorial Ionization Anomaly (EIA) crests between the hemispheres during the main phase of 23 April 2023, geomagnetic storm. The Prompt Penetration Electric Field amplified the intensity of both EIA crests. However, the enhancement at the southern crest began to decay within an hour, while the northern crest began to strengthen. Thermosphere‐Ionosphere‐Electrodynamics General Circulation Model simulations indicate that trans‐equatorial wind played a key role in these variations. Wavelet periodograms of ground‐based Total Electron Content measurements confirmed the presence of Traveling Ionospheric Disturbances (TIDs). Storm‐induced winds and TIDs likely changed the altitude of the F‐peaks and the recombination rates between crests, and plasma transport by trans‐equatorial winds also contributed to this rare phenomenon.