:Issued: 2026 Sep 01 1808 UTC :Product: documentation at http://www.sidc.be/products/bul #--------------------------------------------------------------------# # SIDC Weekly bulletin on Solar and Geomagnetic activity # #--------------------------------------------------------------------# WEEK 1339 from 2026 Aug 24 Solar Active Regions (ARs) and flares --------------- Solar flaring activity was at low to moderate levels at the beginning of the week, increased to high levels on August 25, and remained low from August 27 onwards. Over the course of the week, twenty-one C-class flares and seven M-class flares were recorded, with no X-class flares. Seven active regions were observed on the visible solar disk over the week. SIDC Sunspot Group 929 (NOAA Active Region 4513) was the main driver of the flaring activity throughout the week and produced all M-class flares. The region was the most complex active region on the solar disk at the beginning of the week, with a beta-gamma-delta magnetic configuration, before gradually decreasing in magnetic complexity towards the end of the week. The largest flare was an M6.9 flare (SIDC Flare 8465), peaking at 10:02 UTC on August 25, associated with SIDC Sunspot Group 929. Type II radio emission was detected at 09:59 UTC during this flaring activity. Low-level C-class flaring was also produced by SIDC Sunspot Group 948 (NOAA Active Region 4517), SIDC Sunspot Group 949 (NOAA Active Region 4518), and active regions behind the east limb. Coronal mass ejections --------------------- Several coronal mass ejections (CMEs) were detected in the available coronagraph imagery over the past week, one of which was estimated to have a possible Earth-directed component. SIDC CME 714 was detected in SOHO/LASCO-C2 coronagraph data from around 11:00 UTC on August 25, directed primarily towards the east from Earth's perspective and associated with the M6.9 flare, produced by SIDC Sunspot Group 929. A glancing-blow arrival at Earth was expected on August 28. However, no clear ICME signature associated with this CME were identified in the available solar wind data. A halo CME (SIDC CME 715) was observed in SOLAR-1/CCOR-2 coronagraph imagery from around 18:00 UTC on August 27. This CME was deemed to be backsided, and no impact on the solar wind conditions near Earth was expected. No other Earth-directed CMEs were detected in the available coronagraph imagery over the past weeks. Coronal Holes --------------------- A positive polarity coronal hole (SIDC Coronal Hole 159) started to cross the central meridian on August 24. Proton flux levels --------------------- The greater than 10 MeV proton flux, as measured by GOES-18 and GOES-19, remained below the 10 pfu threshold throughout the week. It was slightly elevated at the beginning of the week, but stayed well below the threshold and returned to near-background levels by mid-week. Electron fluxes at GEO --------------------- The greater than 2 MeV electron flux, as measured by GOES-18 and GOES-19, was fluctuating around the 1000 pfu alert threshold during the first part of the week, mainly until August 28, and remained below the threshold for the rest of the week. The 24-hour electron fluence was at moderate levels at the beginning of the week and decreased to normal levels towards the end of the period. Solar wind --------------------- At the beginning of the week, solar wind parameters reflected slow solar wind conditions. The solar wind speed decreased from about 390 km/s to around 260 km/s by August 27. The interplanetary magnetic field remained weak, below 6 nT, and the magnetic field orientation was predominantly in the negative sector, with the field directed towards the Sun. From August 28 until the end of the week, solar wind conditions were slightly disturbed. The interplanetary magnetic field reached values up to about 14 nT on August 29, and the north–south component of the interplanetary magnetic field, Bz, reached a minimum value of about -13 nT. The solar wind speed gradually increased from about 290 km/s to around 470 km/s by August 30. The magnetic field orientation was predominantly in the positive sector, with the field directed away from the Sun. These slightly disturbed solar wind conditions were most likely associated with the high-speed stream influence from the positive polarity coronal hole SIDC Coronal Hole 159. Geomagnetism --------------------- Geomagnetic conditions were quiet to unsettled at the start of the week (NOAA Kp = 1 to 3; K-Bel = 1 to 3). From late August 28 until the end of the week, geomagnetic conditions became mostly unsettled to active both globally and locally over Belgium, following the arrival of a high-speed stream from the positive polarity coronal hole SIDC Coronal Hole 159. --------------------------------------------------------------------------- DAILY INDICES DATE RC EISN 10CM Ak BKG M X 2026 Aug 24 085 088 143 006 B6.9 1 0 2026 Aug 25 086 082 132 004 B7.7 4 0 2026 Aug 26 095 085 131 002 B6.1 2 0 2026 Aug 27 084 083 122 002 B4.6 0 0 2026 Aug 28 091 077 116 018 B4.2 0 0 2026 Aug 29 /// 076 111 020 B4.3 0 0 2026 Aug 30 /// 070 107 017 B4.7 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 24 1851 1936 1954 N06E12 M1.7 1B 13/4513 25 0104 0126 0140 N03E11 M1.9 1N 13/4513 25 0355 0402 0407 N04E14 M1.0 SN 13/4513 25 0630 0640 0646 N04E12 M1.8 1N 13/4513 25 0932 1002 1013 N03E06 M6.9 1B 13/4513 II/3 26 0629 0634 0638 N04E15 M2.2 1B 13/4513 III/1II/2 26 1206 1214 1222 N05W05 M1.0 SF 13/4513 #--------------------------------------------------------------------# # 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 # #--------------------------------------------------------------------#