Features Investigates of the geospace storm over China During May 10–12, 2024

Abstract. This study investigates the characteristics of geomagnetic and ionospheric disturbances over China associated with the intense geospace storm that occurred during May 10–12, 2024. Observations were conducted using data from nine Intermagnet observatories, four ionosondes, and multiple satellites from the GNSS. To examine the quasi-periodic temporal variations of magnetic field components, this study introduces systems spectral analysis exclusively. The analysis reveals that the geospace storm, classified as a severe event, was accompanied by both intense geomagnetic perturbations and significant negative ionospheric storms. During the geomagnetic storm, the peak-to-peak amplitude of variations in the X-, Y-, and Z-components reached 550–800 nT, 166–422 nT, and 100–412 nT, respectively. The duration of the geomagnetic storm was approximately 40–60 h. The fluctuation spectrum of the geomagnetic field predominantly featured components with periods of 200 min and 90 min. During the negative ionospheric storm, which lasted around 50 h, foF2 values decreased by 2–3 times, while electron density values decreased by 4–9 times. At the same time, hmF2 values increased by 200–300 km. Other ionogram parameters exhibited minor changes. Total electron content values during the storm decreased by 30–40 TECU during the day (by 2–3 times) and by 10 TECU at night (by 2 times). The causes leading to the negative ionospheric storm was primarily driven by the penetration of magnetospheric electric fields into the ionosphere, the enhancement of plasma convection, disturbances in the thermospheric chemical composition, the intensification of thermospheric winds, and plasma transport processes occurring in both vertical and horizontal directions.