Abstract

not-yet-known not-yet-known not-yet-known unknown This study investigates the F-region plasma density and irregularities response during the May-2024 geomagnetic storm using data from Swarm and GRACE-FO missions. While Swarm-B provided measurements at 11/23 LTs, data from GRACE-FO and Swarm-A were collected at 05/17 LTs and 07/19 LTs, respectively. Following the storm commencement on May 10, the equatorial ionization anomaly (EIA) was particularly strong (depleted) on the dayside (nightside). Additionally, an unexpected development of the EIA was observed in the early morning 05/07 LTs. Deviations during the storm’s initial and recovery phases indicate the strong influence of penetration and disturbance dynamo electric fields. Significant equatorial plasma density depletion (EPD) activity with apex altitudes reaching up to ~ 5000 km during pre-midnight on May 11 and ~ 3400 km in the early morning was also noticed. We suggest that the morning EPDs are locally generated rather than being remnants from the previous night.