:Issued: 2025 Sep 30 1401 UTC :Product: documentation at http://www.sidc.be/products/bul #--------------------------------------------------------------------# # SIDC Weekly bulletin on Solar and Geomagnetic activity # #--------------------------------------------------------------------# WEEK 1291 from 2025 Sep 22 Solar Active Regions (ARs) and flares --------------- Solar flaring activity was at moderate levels throughout the week, with forty-eight C-class flares and seven M-class flares observed. The strongest flare was an M6.4 flare (SIDC Flare 5601) peaking at 08:43 UTC on September 28, which was associated with SIDC Sunspot Group 653 (NOAA Active Region 4232, magnetic type beta-gamma). There was a total of twenty-six active regions on the visible disk during the week. SIDC Sunspot Groups 640, 592, 650, 653 (NOAA Active Regions 4217, 4226, 4229, 4232) were the most complex, all with magnetic type beta-gamma. Coronal mass ejections --------------------- A few Coronal Mass Ejections (CMEs) were detected during the week. Almost all of them were either events near the west or east limb or backsided and had no impact on Earth. However, a wide, slow Coronal Mass Ejection (SIDC CME 564) was observed in LASCO/C2 and C3 coronagraph imagery starting from around 02:00 UTC on September 24, lifting off the east limb. A glancing blow arrival, associated with this CME was most likely observed starting from the UTC afternoon on September 28. Coronal Holes --------------------- Two small, equatorial, negative-polarity coronal holes (SIDC Coronal Holes 132 and 133) crossed the central meridian between September 24 and 25. A high-speed stream may have arrived at Earth starting on September 28, though it is unclear which of these coronal holes was associated with it. Proton flux levels --------------------- The greater than 10 MeV proton flux was below the 10 pfu threshold throughout the week. Electron fluxes at GEO --------------------- The greater than 2 MeV electron flux as measured by GOES 18 and GOES 19 was mostly below the 1000 pfu threshold during the week, with short intervals in which it rose above the 1000 pfu threshold. The 24-hour electron fluence was at moderate levels at the beginning of the week and gradually decreased to nominal levels during the week. Solar wind --------------------- The solar wind parameters (ACE) were initially enhanced at the beginning of the week, under the influence of the high-speed stream from the mid-latitude negative polarity coronal hole (SIDC Coronal Hole 126) that crossed the central meridian on September 19. Speed values increased from approximately 300 km/s up to approximately 630 km/s. The interplanetary magnetic field values increased from 2 nT to 18 nT. The Bz component varied between -13 nT and 17 nT. A gradual return to the slow solar wind regime followed. The solar wind conditions (ACE) showed again a mild enhancement on September 28, primarily due to the arrival of a glancing blow, associated with the Coronal Mass Ejection (SIDC CME 564) observed around 02:00 UTC on September 24, and potentially influenced by the high-speed stream associated with (SIDC Coronal Hole 133) that crossed the central meridian on September 25. Speed values increased from approximately 350 km/s to approximately 440 km/s. The interplanetary magnetic field values increased from 5 nT to 11 nT. The Bz component varied between -8 nT and 11 nT. The interplanetary magnetic field angle was mostly in the negative sector during the week. Geomagnetism --------------------- Geomagnetic conditions globally were mostly at quiet to unsettled levels (NOAA Kp 1 to 3), with an interval of active conditions (NOAA Kp 4- ) between 12:00 UTC and 15:00 UTC on September 23. Geomagnetic conditions locally were mostly at quiet to unsettled levels (K BEL 1 to 3) throughout the week. --------------------------------------------------------------------------- DAILY INDICES DATE RC EISN 10CM Ak BKG M X 2025 Sep 22 /// 166 172 014 C1.0 0 0 2025 Sep 23 210 195 171 014 C1.2 1 0 2025 Sep 24 /// 153 184 008 C1.7 2 0 2025 Sep 25 186 156 170 007 C1.4 0 0 2025 Sep 26 /// 150 165 008 C1.2 1 0 2025 Sep 27 /// 142 164 006 C1.5 3 0 2025 Sep 28 /// 166 171 010 C1.6 1 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 23 1024 1034 1038 S14W42 M1.0 SF 22/4217 III/2 24 0916 0931 0944 ////// M1.0 28/4224 24 1857 1913 1922 ////// M1.6 28/4224 26 1949 2001 2007 ////// M1.6 ///4233 II/1 27 0329 0359 0418 S15W10 M1.0 SF 32/4226 VI/2 27 0418 0423 0427 N18E77 M1.1 SF 32/4226 27 0703 0714 0718 N03E71 M1.1 SF ///4232 III/2V/3 28 0834 0843 0849 N03E58 M6.4 1 ///4232 III/3V/3 #--------------------------------------------------------------------# # 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 # #--------------------------------------------------------------------#