:Issued: 2025 Aug 20 2029 UTC :Product: documentation at http://www.sidc.be/products/bul #--------------------------------------------------------------------# # SIDC Weekly bulletin on Solar and Geomagnetic activity # #--------------------------------------------------------------------# WEEK 1285 from 2025 Aug 11 Solar Active Regions (ARs) and flares --------------- Solar flaring activity ranged from moderate to low during the past week. Between August 10 and 12, several M-class flares were produced, the strongest being an M2.2 flare (SIDC Flare 5104) peaking at 15:07 UTC on August 10, originating from SIDC Sunspot Group 588 (NOAA AR 4168). Other notable flares included an M1.8 flare (SIDC Flare 5122) from SIDC Sunspot Group 581 (NOAA AR 4165) peaking at 01:23 UTC on August 12, and a series of M1.3-M1.7 flares from Sunspot Groups 588 and 592. After August 13, only C-class flaring was recorded, with the largest being a C7.7 flare (SIDC Flare 5156) from SIDC Sunspot Group 590 (NOAA AR 4172) peaking at 21:22 UTC on August 15. A maximum of thirteen numbered sunspot groups were visible during the week, decreasing to six by the end of the period. The most complex and productive regions were SIDC Sunspot Group 588 (NOAA AR 4168, Beta-Gamma-Delta), responsible for most of the early M-class flaring before rotating over the west limb, and SIDC Sunspot Group 590 (NOAA AR 4172, Beta-Gamma then Beta), which remained flare-productive throughout the week. SIDC Sunspot Group 596 (NOAA AR 4178, Beta-Gamma then Beta) also contributed. Coronal mass ejections --------------------- Several CMEs were observed during the week, mostly associated with activity near the west limb and therefore not Earth-directed. A large CME was recorded on August 10 at 14:48 UTC with a speed of about 638 km/s, most likely linked to eruptive activity from SIDC Sunspot Group 592 (NOAA AR 4173). Additional CMEs on August 11-12 were linked to Sunspot Groups 588 and 592 after they rotated behind the west limb. Coronal Holes --------------------- Several coronal holes transited the central meridian during the week. SIDC Coronal Hole 123 (elongated, southern, positive polarity) continued to cross the central meridian from August 6 onward and influenced solar wind conditions for much of the week. SIDC Coronal Hole 124 (small, northern, positive polarity) and SIDC Coronal Hole 125 (small, equatorial) contributed to enhanced streams during August 11-12. SIDC Coronal Hole 116 (mid-latitude, negative polarity) returned on August 12 and transited the central meridian on August 15. Finally, SIDC Coronal Hole 104 (polar-south, positive polarity) also reached the central meridian on August 14. Proton flux levels --------------------- The >10 MeV proton flux remained below the 10 pfu threshold throughout the week. Slight enhancements were considered possible due to the number of active regions, but no significant events were recorded. Electron fluxes at GEO --------------------- The >2 MeV electron flux, measured by GOES 18 and 19, remained elevated and frequently exceeded the 1000 pfu threshold, particularly in response to the persistent high-speed streams from coronal holes. The 24-hour electron fluence was at moderate levels during most of the week. Solar wind --------------------- Solar wind conditions were enhanced early in the week due to high-speed streams associated to the SIDC Coronal Holes 123 and 125. Speeds reached up to 634 km/s on August 12. The total interplanetary magnetic field (Bt) peaked around 8.5 nT, with the southward interplanetary magnetic field component (Bz) fluctuating between -6 and +7 nT. From August 14-15, the solar wind gradually weakened toward a slow regime, with speeds between 340 and 500 km/s and the total interplanetary magnetic field (Bt) around 5-6 nT. By August 16-17, solar wind remained slow (around 307-400 km/s), but high-speed streams from SIDC Coronal Hole 116 were forecast to arrive on the follow up week due to its location (mid-latitude) and its transition of the central meridian on August 15. Geomagnetism --------------------- Geomagnetic activity was mostly unsettled to active at the beginning of the week, with NOAA Kp indices up to 4 and local Belgian K-index reaching 4. This was due to sustained high-speed stream influence combined with long periods of negative southward interplanetary magnetic field component (Bz). From August 13-15, conditions eased to quiet to unsettled, with occasional active intervals linked to residual streams. By August 16-17, geomagnetic activity was quiet, with NOAA Kp between 1-2 and Belgian K-index between 1-3. --------------------------------------------------------------------------- DAILY INDICES DATE RC EISN 10CM Ak BKG M X 2025 Aug 11 /// 181 146 020 C2.8 3 0 2025 Aug 12 /// 172 152 017 C1.8 2 0 2025 Aug 13 /// 183 140 020 C1.0 0 0 2025 Aug 14 /// 170 130 012 B6.4 0 0 2025 Aug 15 /// 143 123 010 B5.9 0 0 2025 Aug 16 /// 124 122 008 B5.8 0 0 2025 Aug 17 /// 083 117 006 B6.7 0 0 --------------------------------------------------------------------------- # RC : Sunspot index (Wolf Number) from Catania Observatory (Italy) # EISN : Estimated International Sunspot Number # 10cm : 10.7 cm radioflux (DRAO, Canada) # Ak : Ak Index Wingst (Germany) # BKG : Background GOES X-ray level (NOAA, USA) # M,X : Number of X-ray flares in M and X class, see below (NOAA, USA) --------------------------------------------------------------------------- NOTICEABLE EVENTS SUMMARY DAY BEGIN MAX END LOC XRAY OP 10CM Catania/NOAA RADIO_BURST_TYPES 11 0342 0352 0359 ////// M1.3 78/4173 11 1420 1435 1457 N02W86 M1.5 SF 75/4168 11 1518 1536 1551 ////// M1.6 75/4168 12 0042 0059 0118 ////// M1.5 /////// III/2 12 0118 0123 0127 ////// M1.8 /////// III/2 #--------------------------------------------------------------------# # Solar Influences Data analysis Center - RWC Belgium # # Royal Observatory of Belgium # # # # Website http://www.sidc.be. # # E-mail sidc-support@oma.be # # To unsubscribe http://www.sidc.be/registration/unsub.php # # # # Legal notices: # # - Intellectual Property Rights: # # http://www.astro.oma.be/common/internet/en/data-policy-en.pdf # # - Liability Disclaimer: # # http://www.astro.oma.be/common/internet/en/disclaimer-en.pdf # # - Use and processing of your personal information: # # http://www.astro.oma.be/common/internet/en/privacy-policy-en.pdf # #--------------------------------------------------------------------#