Abstract

The Nmax observations from Global-scale Observations of the Limb and Disk (GOLD) satellite report for the first time a unique transition of asymmetric Equatorial Ionization Anomaly (EIA) crest from south to north within a short duration of 1.7 hours during the main phase of 23 April 2023 geomagnetic storm. The Prompt Penetration Electric Field occurred on this day produced a superfountain, manifesting an enhancement in EIA crests. The movement of Nmax along a fixed longitude confirmed the transition rate of 650 m/s, which falls under the velocity range of Large Scale Travelling ionospheric Disturbances (LSTIDs). The wavelet periodogram of GPS-TEC over EIA crest and trough revealed an enhanced periodicity of 1.2 hour indicating the presence of LSTID during the period when EIA exhibited the transition. These unique observations indicate the importance of assessing the impact of storms on large-scale plasma processes prevailing over the equatorial/low-latitude ionosphere.