Effects of solar flares and geomagnetic superstorm on 10 May 2024 in variations of the Doppler frequency shift of the ionospheric signal, geomagnetic field, and telluric current

On 10 May 2024, one of the strongest geomagnetic storms for the last 67 years occurred. The highest level of G5 geomagnetic activity was recorded for two days. The storm began after a cloud of cosmic plasma, which was ejected from the Sun as a result of several flares on May 8 with an intensity ranging from X1.0 to M8.6 (www.xrus.ru), arrived at Earth. During such flares, the intensity of the Sun X-ray and ultraviolet (UV) radiation increases sharply. This leads to an increase in the electron concentration in the ionosphere. The X1.0 flare, which occurred in the time interval 01:33 - 01:48 UT with a maximum at 01:41 UT, caused a clear response in the Doppler frequency shift (DFS) of the ionospheric signal. The amplitude of the DFS disturbances was 4.5 Hz, lasting about 800 seconds. The delay in the appearance of the disturbance in the DFS in response to the impact of ionizing radiation was approximately 60 seconds.  The disturbances were then recorded in the magnetic field by an induction magnetic sensor (IMS-008) and subsequently by a fluxgate magnetometer (LEMI-008). These disturbances were only observed on the sun side of the Earth. Measurements showed that the response in the geomagnetic field to the X1.0 solar flare was initiated by the modulation of electric currents in the ionosphere as a result of changes in the electron concentration.
During the interaction of the solar wind with the magnetosphere, orbital and ground-based magnetic observatories recorded a magnetic pulse characterizing Storm Sudden Commencement (SSC). The storm sudden commencement was recorded on 10 May 2024 at 17:06 UT. The magnetic storm immediately exceeded the G4-level and intensified to the maximum G5-level, Dst index reached values of 412 nT. The planetary index of geomagnetic disturbance reached its highest values Kp=9 on 10 - 11 May. The decline in geomagnetic activity, which began on May 12, ended by midday on May 13. A well-defined reaction of the ionosphere in the DFS began almost simultaneously with the growth of the Kp and Dst indices, which characterize the level of disturbance of the geomagnetic field. The high temporal resolution of the induction magnetometer IMS-008 (sampling frequency f = 66.6 Hz) allowed us to determine the time of the SSC as 17:05:31 UTC. At 14 seconds later, the SSC was registered by the fluxgate magnetometer LEMI-008. The disturbances in the telluric current variations manifested 2-3 seconds after those recorded by the induction magnetometer. 
Using the example of the X1.0 solar flare (08.05.2024) and the May 2024 G5-level extreme geomagnetic storm: the temporal features and differences in the directionality between the processes of the magnetosphere, ionosphere and telluric currents interactions are traced.
 

This research was funded by the Science Committee of the Ministry of Science and Higher Education of the Republic of Kazakhstan, grant number AP19678127  ”Development of the methods for geophysical fields monitoring in the lithosphere-atmosphere-ionosphere-magnetosphere system in a seismically hazardous region of Northern Tien Shan”.