| Popis: |
On 4 November 2021 it was detected the most intense geomagnetic storm that occurred so far during the rising phase of solar cycle 25 (Kp=8-). This work summarizes the state of the solar wind before and during the geomagnetic storm, the response of the plasmasphere-ionosphere-thermosphere system in the European sector and, for a comparison, the ionosphere-thermosphere response of the American sector. The plasmasphere dynamics was investigated through field line resonances detected at the European quasi-Meridional Magnetometer Array. The ionosphere was investigated through the combined use of ionospheric parameters (foF2, hmF2) from ionosondes and Total Electron Content (TEC) obtained from Global Navigation Satellite System receivers at four locations in the European sector and three locations in the American sectors. Aeronomic parameters were retrieved by using an original method based on the observed electron concentration in the ionospheric F region. The behavior of foF2 and TEC data is also discussed, speculating about the possible interconnection between the topside ionosphere and the plasmasphere at the investigated European sites. Experimental results can be summarized as it follows: a) The plasmasphere, originally in a state of saturation, was eroded up to two Earth’s radii, and only partially recovered after the main phase of the storm, and a possible formation of a drainage plume is also observed; b) The ionospheric parameters showed phases characterized by negative and positive variations, with longitudinal and latitudinal dependence of storm features in the European sector; c) Negative storm signature in electron concentration at the F2 region is also observed in the American sector. This result is mainly attributable to the neutral composition and temperature variations. |
