Intense solar activity near the limbs: monitoring AR4513

ATel #17998; C. Sigismondi (ICRANet, Pescara and APRA, Rome), A. Ravagnin (UAI, Romano d'Ezzelino), P. Ochner (UniPd and INAF, Asiago) , V. Oldani (Stazione Astronomica di Sozzago), A. Brucato (Sapienza University of Rome), A. Reguitti (INAF, Padova), R. Ruffini (ICRANet, Pescara)
on 21 Aug 2026; 18:50 UT
Credential Certification: Andrea Reguitti (andreareguitti@gmail.com)

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After two weeks with the X-ray background down at the B2-B3 level, the solar activity returned to near X-class conditions on 20 August 2026. The renewed activity is primarily associated with the active region AR 4513 at the eastern limb, which produced M2-, M8-, and M3-class flares, followed by additional C-class events on 21 August. Around 15 August, AR 4507 emerged as the dominant active region, generating multiple B- and C-class flares in apparent sympathetic activity with AR 4506. On 21 August, AR 4507 produced a long-duration M1.7 event at the western limb. The event began at 09:09 UT, persisted for more than five hours, and represents the most energetic episode attributed to this region to date. The energetic integral is larger than 0.15 J/m^2 and it is comparable with the most intense X-class flares. The monitoring for white-light flare signatures in limb events was continued (ATel#17763 and ATel#17494), because of their proximity with the limb. Particular attention was paid to the facular structures of AR 4513 and complementary inspection of SDO/HMI imagery was performed. No white-light signatures were identified, including in observations obtained with the ICRANet PHYSIS 80 mm refracting telescope in Lanciano, Italy, during the two flares of 20 August at 12:00 UT and 16:10 UT, both at M3-level of X-ray flux. Further high-quality white-light observations are therefore strongly encouraged. AR 4513 has been classified as a Beta-Gamma-Delta region; however, the principal flaring structures appear to exhibit lifetimes of approximately three days, roughly two years after the maximum of Solar Cycle 25 (ATel#17852, ATel#17879, ATel#17851, and ATel#17852). These observations are important since the most intense X-ray flares may occur even during the descending phase of the solar cycle. In the accompanying link there are some images of the AR 4513 faculae on 20 August 2026 and flares 20-21 August 2026 (SDO - GOES 19 and PHYSIS -80mm telescope)

AR 4513 faculae on 20 August 2026 and flares 20-21 August 2026