МОРФОЛОГІЧНІ ОСОБЛИВОСТІ ДЖЕРЕЛ ЕКСТРЕМАЛЬНИХ ГЕОМАГНІТНИХ БУР

The modern world is becoming increasingly vulnerable to geomagnetic storms due to the rapid development of new technologies and technical systems. This applies to all areas of human activity where power grids, GPS, the Internet, and digital communications are used. Storms can cause damage to the energy sector, aviation, navigation, satellite electronics, communication systems, industry, and the agro-industrial complex. Extreme geomagnetic storms can cause enormous economic damage and endanger to human health. Their prediction is very important, but not yet perfect enough. Extreme geomagnetic storms are typically caused by coronal mass ejections (CMEs) during powerful flares. A detailed study of their sources is very important. To study the conditions that favor the occurrence of extreme storms, we selected six active regions (ARs) that were their sources in the period from 2000 to 2024. We have analyzed the spatial and temporal evolution, morphological characteristics, magnetic field structure, and flare activity of NOAA 09393, 10484, 10486, 10501, 10696, 13664. Some ARs were located in large activity complexes. The ARs studied developed rapidly, their area and number of spots increased, their magnetic structure became more complex, and the flare activity increased. Many of these ARs had very large maximum areas exceeding 2000 millionths of a solar hemisphere. On the days when the eruptions occurred the ARs were located near the central meridian, and the Bz-component of the interplanetary magnetic field was directed south. Their area and spot number were close to their maximum, the magnetic configuration was βγδ in most cases. The sources of the CMEs were M and X class flares, which were preceded by the rapid emergence of new magnetic fluxes and their reconnection with the existing magnetic field of the region. The most powerful geomagnetic storms during the considered period with a minimum DST index less than -400 nT were observed on November 20, 2003 and May 10–11, 2024. These storms were caused by CMEs from flares occurred in ARs 10501 and 13664. These ARs were characterized by complex magnetic topology and rapid magnetic flux emergence. The storm on May 10–11, 2024, was preceded by cannibal CMEs that enhanced its strength and duration. The most powerful storm of the period under review, on November 20, 2003, with a peak Dst index of -422 nT, was caused by a CME from an M3.9 flare in the AR NOAA 10501. During the storm’s peak, auroras were observed as far south as Florida, Michigan, and Wisconsin in the United States and Greece in Europe. It was found that AR with a small area and moderate flares can produce extreme storms, while ARs with large areas and with powerful flares do not always.