The presented work examines the extreme geomagnetic storm that occurred during May 10–12, 2024, following solar flares on May 8–9, 2024, hence named the Victory Day Storm. This event, marked as the most intense geomagnetic storm of the 21st century to date, caused significant disturbances not only in the auroral zone but also in the subauroral and mid-latitude ionosphere. Using data from satellites, ground-based ionosondes, Global Navigation Satellite System (GNSS) receivers, and all-sky cameras located in the Kaliningrad region, this research tracks how the coronal mass ejection from the Sun led to substantial changes in ionospheric plasma density, structure, and dynamics. Notably, auroras were observed in the subauroral and mid-latitudes, which is a rare phenomenon at these latitudes, providing valuable information on the ionospheric response to extreme geomagnetic activity. Swarm and DMSP satellite data identified polarization jet/SAID as U-shaped structures on ionograms, while Strong Thermal Emission Velocity Enhancements (STEVE) was observed by an all-sky camera along with increased Rate of Total Electron Content Index (ROTI). A diffuse aurora with a moving omega structure, as well as ray and corona auroral features, were observed, accompanied by a significant ROTI increase and enhanced scattering of the auroral Es layer on ionograms.

This study presents a comprehensive analysis of the impact of Storm Laura, which was observed over Europe and the Baltic Sea on 12 March 2020, on the thermosphere–ionosphere system. The investigation of ionospheric disturbances caused by the meteorological storm was carried out using a combined modeling approach, incorporating the regional AtmoSym and the global GSM TIP models. This allowed for the consideration of acoustic and internal gravity waves (AWs and IGWs) generated by tropospheric convective sources and the investigation of wave-induced effects in both the neutral atmosphere and ionosphere. The simulation results show that, three hours after the activation of the additional heat source, an area of increased temperature exceeding 100 K above the background level formed over the meteorological storm region. This temperature change had a significant impact on the meridional component of the thermospheric wind and total electron content (TEC) variations. For example, meridional wind changes reached 80 m/s compared a the meteorologically quiet day, while TEC variations reached 1 TECu. Good agreement was obtained with experimental TEC maps from CODE (Center for Orbit Determination in Europe), MOSGIM (Moscow Global Ionospheric Map), and WD IZMIRAN (West Department of Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation Russian Academy of Sciences), which revealed a negative TEC value effect over the meteorological storm region.

We study the spatiotemporal variations of ionospheric parameters over the regions of Eurasia by analyzing data from chains of high- and mid-latitude ionosondes during the extreme magnetic storm in May 2024. The analysis of ionospheric parameters allowed us to note strong latitudinal and longitudinal differences in variations of the analyzed parameters under quiet conditions before the onset of the magnetic storm and during its development. Almost immediately after the onset of the storm at 17:00 UT on May 10, 2024, according to data from all ionosondes, a sharp drop in the electron density at the height of the F2-layer maximum was recorded, regardless of the local time at the measurement point. Ionosondes of the high-latitude chain showed a complete absence of data (radio signal blackout) during the main and early recovery phases of the storm until the evening of May 12, 2024, i.e. more than one and a half days. Additional bursts of geomagnetic activity during the recovery phase of the storm were also accompanied by significant and prolonged decreases in the electron density according to ionosonde measurements at all longitudes of Eurasia. The recovery of ionospheric ionization began on May 14–15 at all longitudes of the mid- and high-latitude regions of Eurasia. A long-term negative disturbance of electron density covering a huge territory of mid-latitude Eurasia was caused by an extraordinary, catastrophic drop in the [O]/[N2] ratio according to satellite measurements of GUVI TIMED during the superstorm for almost three days. The response of the thermospheric composition of neutral gas to the processes developing at high latitudes of the Northern Hemisphere on May 10–15, 2024 was global, with penetration of the thermospheric disturbance at almost all longitudes up to the equatorial latitudes (~10° N) and with very low values of the [O]/[N2] ratio ~0.1÷0.4. Significant differences in the spatiotemporal variations of the thermospheric composition of neutral gas were revealed during the most extreme geomagnetic storms of the current 21st century — in May 2024 and October–November 2003 (Halloween storms). The magnetic superstorm in May 2024 was much more geoeffective than the superstorms in October–November 2003, and caused a significantly different ionospheric response at different longitudes and latitudes of the Northern Hemisphere.

The influence of the meteorological storm in October 2018 in the Baltic Sea on the state of the mesosphere and lower thermosphere is investigated. The wave activity of gravity waves was analyzed using TIMED/SABER satellite data and the effects of the meteorological storm at altitudes of 80–100 km were determined. The wavelet analysis of temperature perturbations revealed two ranges of vertical wavelengths 5–8 km and 14–18 km. In the area of a meteorological storm, the GWs amplitude with vertical wavelengths of 5–8 km increases, and the area of their maximum expands and shifts upward to heights of ~90 km, while on meteorologically calm days these waves are observed at heights of 65–70 km and with smaller amplitudes. Above the meteorological storm region at altitudes of 90–100 km, the values of the gravity waves potential energy density significantly increase compared to calm days before and after the storm, as well as the spatial dimensions of the disturbance region increase.