:Issued: 2026 Oct 19 1524 UTC :Product: documentation at http://www.sidc.be/products/bul #--------------------------------------------------------------------# # SIDC Weekly bulletin on Solar and Geomagnetic activity # #--------------------------------------------------------------------# WEEK 1346 from 2026 Oct 12 Solar Active Regions (ARs) and flares --------------- Solar flaring activity was at low to moderate levels throughout the week, with thirty-seven C-class flares and one M-class flare observed. No X-class flares were recorded. The strongest flare was an M1.3 flare (SIDC Flare 8750), peaking at 15:42 UTC on October 16, which was associated with SIDC Sunspot Group 980 (NOAA Active Region 4551, magnetic type beta-gamma). SIDC Sunspot Group 980 was among the most complex regions during the week, reaching a beta-gamma-delta magnetic configuration. Other notable regions included SIDC Sunspot Group 976 (NOAA Active Region 4549), which rotated behind the west limb, and SIDC Sunspot Group 966 (NOAA Active Region 4557), which rotated on disk from the east limb. A total of fourteen numbered active regions were observed on the visible solar disk during the week. Coronal mass ejections --------------------- A wide Coronal Mass Ejection (SIDC CME 730) was observed in LASCO/C2 coronagraph imagery starting from around 23:15 UTC on October 11, directed mainly eastward. It was likely associated with EUV dimming observed in the southeast quadrant. Preliminary analysis indicated a possible glancing blow arrival at Earth late on October 14. A possible weak solar wind enhancement was observed around 17:30 UTC on October 14, although its association with the CME remained uncertain. The other observed CMEs were not expected to impact Earth. Coronal Holes --------------------- A recurrent mid-latitude, negative-polarity coronal hole (SIDC Coronal Hole 142) was located near the central meridian at the beginning of the week. An associated high-speed stream arrived at Earth around October 13–14. A recurrent mid-latitude, positive-polarity coronal hole (SIDC Coronal Hole 159) started crossing the central meridian around October 17. An associated high-speed stream was expected to arrive at Earth around October 20. Proton flux levels --------------------- The greater than 10 MeV proton flux remained below the 10 pfu threshold throughout the week. Electron fluxes at GEO --------------------- The greater than 2 MeV electron flux measured by GOES 18 and GOES 19 remained mostly below the 1000 pfu threshold throughout the week. Brief increases around or slightly above the threshold were observed, particularly in GOES 18 data on October 15. The electron flux subsequently decreased and remained below the threshold towards the end of the week. The 24-hour electron fluence was generally at normal levels, with occasional values approaching moderate levels. Solar wind --------------------- The solar wind parameters reflected slightly perturbed conditions at the beginning of the week, with possible signatures of a glancing blow associated with SIDC CME 729 around October 12–13. Solar wind speed ranged between approximately 450 km/s and 540 km/s, while the interplanetary magnetic field reached values up to about 16 nT. A stronger enhancement followed under the influence of the high-speed stream associated with the negative-polarity SIDC Coronal Hole 142. Solar wind speeds increased to approximately 650–670 km/s around October 13–14. An additional, short-lived enhancement was observed around 17:30 UTC on October 14, with the solar wind speed increasing to approximately 610 km/s, possibly associated with a glancing blow from SIDC CME 730. During the second part of the week, solar wind conditions gradually returned towards a slow solar wind regime, with speeds decreasing to approximately 400–450 km/s by the end of the week. Geomagnetism --------------------- Geomagnetic conditions globally and locally were mostly at quiet to unsettled levels throughout the week, with isolated active intervals. The enhanced solar wind conditions associated with the high-speed stream from SIDC Coronal Hole 142 contributed to increased geomagnetic activity during the middle of the week. Global geomagnetic conditions reached active levels, with NOAA Kp reaching 4-. Locally, active conditions were observed on several occasions, with K BEL reaching 4. During the second part of the week, geomagnetic conditions gradually returned towards mostly quiet levels globally and locally, as the high-speed stream influence weakened. --------------------------------------------------------------------------- DAILY INDICES DATE RC EISN 10CM Ak BKG M X 2026 Oct 12 /// 089 123 008 B5.5 0 0 2026 Oct 13 056 065 136 012 B6.4 0 0 2026 Oct 14 /// 101 123 012 B5.8 0 0 2026 Oct 15 073 072 126 012 B5.4 0 0 2026 Oct 16 092 081 131 017 B6.7 1 0 2026 Oct 17 /// 072 132 008 B6.0 0 0 2026 Oct 18 /// 068 137 006 B5.2 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 16 1538 1542 1545 ////// M1.3 63/4551 #--------------------------------------------------------------------# # 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 # #--------------------------------------------------------------------#