:Issued: 2025 Sep 09 1547 UTC :Product: documentation at http://www.sidc.be/products/bul #--------------------------------------------------------------------# # SIDC Weekly bulletin on Solar and Geomagnetic activity # #--------------------------------------------------------------------# WEEK 1288 from 2025 Sep 01 Solar Active Regions (ARs) and flares --------------- The Solar flaring activity was at low to moderate levels throughout the week, with 30 C-class flares and 3 M-class flares observed. There were 15 sunspot groups observed on the visible solar disk. SIDC SG 624 (NOAA AR 4207) and SIDC SG 614 (NOAA AR 4197) produced most of the flaring activity. SIDC SG 614 (NOAA AR 4197) rotated off the visible disk at the end of the week. The largest flare was an M1.4-flare (SIDC Flare 5430), with peak time 01:16 UTC on September 05 and was associated with SIDC SG 624 (NOAA AR 4207). Coronal mass ejections --------------------- A Coronal mass ejection (CME) was seen in LASCO-C2 data at 02:24 UTC on September 03, which is associated with a filament eruption seen in SDO/AIA 194 and 304 at 01:28 UTC on September 03 on the northwest quadrant of the solar disk. A faint halo CME was seen in LASCO-C3 data at 20:36 UTC on September 04, which is associated with an eruption in SDO/AIA 304 at 19:22 UTC on September 04 near the center of the solar disk. Coronal Holes --------------------- Three positive polarity coronal holes crossed the meridian during the week. Returning, equatorial SIDC Coronal Hole 123 first reached the central meridian on September 02 (Other crossing times: August 06); Equatorial SIDC Coronal Hole 128 first reached the central meridian on September 03 and equatorial SIDC Coronal Hole 129 first reached the central meridian on September 04. The high-speed stream (HSS) associated with SIDC Coronal Hole 123 reached the Earth on September 06. Proton flux levels --------------------- The greater than 10 MeV GOES proton flux became elevated at the start of the week but remained below the 10 pfu threshold until September 02 due to a CME that left the Sun on August 30. The 10 MeV GOES proton flux remained at nominal levels for the rest of the week. Electron fluxes at GEO --------------------- The greater than 2 MeV electron flux, as measured by the GOES-19 was above the 1000 pfu threshold between 18:55 UTC and 22:50 UTC on September 05. The greater than 2 MeV electron flux, as measured by the GOES-18 was below the threshold throughout the week. The 24-hour electron fluence was at nominal levels throughout the week. Solar wind --------------------- At the beginning of the week solar wind conditions at Earth were mildly disturbed under the waning influence of a high-speed stream (HSS) associated with SIDC Coronal Hole 122. They became disturbed by the arrival of an ICME on September 01 at 20:20 UTC, by September 04 they had returned to slow solar wind conditions. On September 05 the solar wind conditions gradually started to enhance due to the arrival of a high-speed stream associated with SIDC Coronal Hole 123 and they became more disturbed by the arrival of an ICME on September 06 at 13:50 UTC. This ICME is probably associated with the CME seen on September 03 but could also be associated with the CME from September 04. The solar wind speed ranged between 345 km/s and 857 km/s. The total interplanetary magnetic field ranged between 2 nT and 27 nT, with the Bz reaching a minimum of – 23 nT. The phi-angle was in the negative sector until September 02 when it switched to the positive sector for the rest of the week. Geomagnetism --------------------- The geomagnetic conditions reached moderate storm conditions globally (Kp 6) and minor storm conditions locally (K BEL 5) at the start of the week under the influence of the first ICME, by September 03 they had returned to quiet to unsettled conditions. They reached minor storm levels globally and locally (Kp 5 nd K BEL 5) on September 06 under the influence of a high-speed stream and the second ICME arrival. The period ended with quiet geomagnetic conditions. --------------------------------------------------------------------------- DAILY INDICES DATE RC EISN 10CM Ak BKG M X 2025 Sep 01 198 189 202 020 C1.6 0 0 2025 Sep 02 180 172 187 028 C1.2 0 0 2025 Sep 03 144 149 180 013 C1.4 0 0 2025 Sep 04 162 165 172 012 C1.5 1 0 2025 Sep 05 151 147 149 009 C1.2 1 0 2025 Sep 06 /// 113 146 024 C1.2 1 0 2025 Sep 07 /// 096 133 004 C1.2 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 04 1336 1344 1349 N30E08 M1.0 1B 08/4207 05 0108 0116 0121 N28W00 M1.4 1N 08/4207 III/2VI/2 06 2207 2215 2217 ////// M1.2 ///4207 #--------------------------------------------------------------------# # 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 # #--------------------------------------------------------------------#