Unusual Storm-time Suppression of the Equatorial Ionization Anomaly (EIA) over the Indian Longitudinal Sector during the 10-11 May 2024 Super Geomagnetic Storm

This study investigates Equatorial Ionization Anomaly (EIA) characteristics over the Indian longitudinal sector during 10–11 May 2024 super geomagnetic storm. Multi-instrument and model approaches were adopted by using data from Advanced Composition Explorer, SWARM-A, TIMED/ GUVI satellites, World Data Centre and the University of Colorado's penetration electric field model data. The geomagnetic storm was driven by cannibal CMEs that originated from the giant sunspot AR3664. Over the Indian longitudinal sector, the observed negative response of the storm led to coalesce of the EIA structure around the magnetic equator. The orientation of Prompt Penetration Electric Fields (PPEFs) and Disturbance Dynamo Electric Fields (DDEFs) and their attendant influence are the determinant factors responsible for ionospheric responses to geomagnetic storms. The observed negative ionospheric response to the storm over the Indian longitudinal sector was as a result of significant enhancements in thermospheric ion recombination to cause electron plasma density depletion.