Уear of publication: 2025

The spatio-temporal variations in ionospheric, geomagnetic and atmospheric parameters over Eurasia were studied based on data obtained during the extreme magnetic storm in May 2024 from high- and mid-latitude chains of ionosondes and magnetometers belonging to INTERMAGNET and Russian observatories. Analysis of the F2-region critical frequencies and their relative deviations from the mean (based on ionosonde measurement data), and the standard deviations of the components of the surface main geomagnetic field (GMF) (based on magnetometer measurement data) enabled us to distinguish strong latitudinal and longitudinal differences in specific features of variations in geophysical parameters, both under quiet conditions before the magnetic storm onset and during the storm. With the onset of the magnetic storm, variability of GMF components was more pronounced in midlatitudes and increased by an order of magnitude: from 80 to 800 for H-component, and from 60 to 600 nT for Z-component. Longitudinal distribution of GMF variations clearly distinguishes longitudes with maximum and minimum intensity of variations. Almost immediately after the storm began at 17:00 UT on 10 May 2024, according to measurements from all ionosondes, a drop in electron concentration was detected at the height of F2-layer maximum regardless of the measurement point local time. During the storms main phase (late 10 May and early 11 May 2024) until the evening of 12 May 2024, total radio blackouts exceeding one-and-a-half days occurred at every high-latitude ionosonde. Thus, strong effects of a negative ionospheric storm were noted in both high-and mid-latitude regions during the main and early recovery phases of the magnetic storm. Additional bursts of geomagnetic activity in the storms recovery phase in certain time intervals on 1113 May 2024 were also followed by significant and long-lasting decreases in electron concentration. At high latitudes, there was a radio blackout for several hours during the transition from 12 to 13 May 2024. From the second half of May 13, the electron concentration began to increase to the pre-storm level, which continued until May 1415 at all longitudes of the mid- and high-latitude region of Eurasia. At the end of the magnetic storm recovery phase, from the second half of day on 14 May and 15 May 2024, a so-called aftereffect of geomagnetic storm (time interval of increased electron concentration) was observed according to the data the mid- and high-latitude ionosondes over Eurasia. The fact of observing this phenomenon in the high latitude region is unusual and very remarkable. Also, a very interesting fact is that longitudinal regions with strong negative variations for 1012 May 2024 match those with enhanced variations in GMF components during the magnetic storm. A long-term negative disturbance of electron concentration covering a huge territory of mid-latitude Eurasia, was induced by an extraordinary, catastrophic drop in the density ratio [O]/[N2] according to GUVI TIMED satellite measurements during the superstorm for almost three days.