Geospace response to May 2024 X-class flare and coronal mass ejection

The space weather events from May 8–12, 2024, including solar flares and a coronal mass ejection, significantly impacted the Earth’s magnetosphere, ionosphere and thermosphere system. These events also affected space technologies such as Global Navigation Satellite Systems (GNSS). On the May 10 post-noon period, a large amount of solar wind energy was transferred to the dayside Earth magnetosphere through the southward Bz-directed interplanetary magnetic field (IMF), initiating a sudden storm commencement (SSC) which reached a minimum DST of −412 nT on May 11. A recovery phase was extended to 12 May. The storm was the strongest since 2002. During the storm’s early recovery phase on May 11, there was a negative ionospheric response of the Total Electron Content (TEC) in all six stations, although more pronounced in the mid-latitude stations than the equatorial stations, leading to an improved GNSS positioning accuracy. This negative TEC response could be explained by changes in the composition of ∑ O / N 2 in the thermosphere. In the Southern Hemisphere, the equatorward flow of the predominant N 2 in the thermospheric circulation occurs before it arrives in the Northern Hemisphere.