EVOLUTION AND FLARE ACTIVITY OF CARRINGTON-CLASS SOLAR ACTIVE REGION NOAA 13664 AND ITS IMPACT ON THE EARTH

We have analyzed the temporal and spatial evolution and the flare activity of the active region (AR) NOAA 13664 and its impact on the Earth. The large group of sunspots that formed it definitely belonged to the Carrington class. The region appeared in the southern hemisphere of the solar disk on 2024 May 1. The number of sunspots was growing rapidly and its area increased from 40 to 2400 millionths of the solar hemisphere. The AR had a complex multipolar configuration of the magnetic field beginning on May 7. On May 8, solar flares of intensity X1.0, M8.7 and M9.9 took place in it, which caused coronal mass ejections (CMEs). These CMEs reached the Earth on May 10, causing strong and extreme geomagnetic storms with bright and very long-lasting auroras. The event was classified as a G5 geomagnetic storm, making it the most intense storm since 2003. On May 9-11, flares of intensity X2.3, X1.5, X4, and X5.8 occurred, each of which caused a CME. The radiation from the X5.8 flare caused a deep shortwave radio blackout over the Pacific Ocean. On May 14, an X8.7-class flare occurred on the western limb of the Sun, the most powerful in solar cycle 25 at that time. The CME that formed caused a short-wave radio blackout over America. On May 9 during observations at the Ernest Gurtovenko solar horizontal telescope of the Main Astronomical Observatory of the National Academy of Sciences of Ukraine the X2.3 flare spectrograms in its main phase were obtained. The active region 13664 passed beyond the solar disk and returned on May 29. It has been renumbered as NOAA 13697. On May 31 and June 1 AR produced three X-flares: X1.1, X1.4, and X1.0. Each of them formed CMEs, which reduced the power of shortwave transmissions at all frequencies below 30 MHz. Radiation from M9.8-class flare on June 8 ionized the upper part of the Earth's atmosphere, causing a deep shortwave radio blackout in the western Pacific Ocean. On June 24 AR13664 returned again. This was its 3rd trip across the solar disk. It was renamed as NOAA 13723. Although the sunspot region was already fragmented to a fraction of its former size, its magnetic component continued to produce powerful solar flares. On June 23, M9.3-class flare occurred in AR, CME from which caused a moderate shortwave radio blackout in Western Europe and Africa. In total, AR13664 produced 198 C-class, 87 M-class, and 17 X-class flares during its three passes across the Sun's disk. By studying in detail the evolution of this hyperactive region NOAA 13664 and its impact on Earth, we are improving our ability to predict solar activity and warn of the extreme space weather events it causes.