Ionosphere-Thermosphere System Response During the May 2024 Geomagnetic Storm

The response of the ionosphere-thermosphere system in Europe during the severe geomagnetic storm of May 2024 was investigated. Between May 7 and 11, multiple X-class solar flares and at least five Earth-directed coronal mass ejections (CMEs) were observed. The initial CME impacted Earth at 12:30 PM UTC on May 10, triggering a geomagnetic enhancement and inducing a negative ionospheric storm over mid-latitude European stations, leading to data gaps on May 11 due to the "G condition" (wherein the electron density at the F2 layer maximum equals or falls below that of the F1 layer maximum).

Thermospheric parameters analyzed using the THERION method revealed a 60% increase in neutral [O] density at 300 km altitude and elevated thermospheric temperatures(~50% increase), while column [O] concentrations showed a ~30% decrease. Enhanced equatorward winds, peaking at 79 m/s, were observed between May 10 and 13. Comparative analysis with other longitudinal sectors confirmed significant regional responses, emphasizing the dynamic behavior of the coupled ionosphere-thermosphere system during severe geomagnetic events.