:Issued: 2025 Oct 21 0958 UTC :Product: documentation at http://www.sidc.be/products/bul #--------------------------------------------------------------------# # SIDC Weekly bulletin on Solar and Geomagnetic activity # #--------------------------------------------------------------------# WEEK 1294 from 2025 Oct 13 Solar Active Regions (ARs) and flares --------------- Solar flaring activity was moderate to high over the week. There were 11 numbered regions on disk over the week, but many of this were magnetically simple. SIDC Sunspot Group 639 (NOAA Active Region 4246) was responsible for most of the flaring activity producing multiple M-class flares each day. This region increased in complexity from the start of the week and had magnetic type Beta-Gamma-delta by October 14. The largest flare of the week from this region was an M4.8 flare (SIDC Flare 5780), peaking on October 15 at 04:15 UTC. This region rotated over the west limb on October 18 but continued to produce M-class flares from beyond the limb. SIDC Sunspot group 621 (NOAA Active region 4248) was also a complex region and produced an M2.0 flare (SIDC Flare 5759) peaking on October 14 at 12:47 UTC. Coronal mass ejections --------------------- Four Coronal Mass Ejections (CMEs) with possible Earth directed components were identified. The first CME (SIDC CME 579) was visible to the north in SOHO/LASCO-C2 data from 14:12 UTC October 13 and could be seen more clearly in STEREO-A COR2 data from 14:23 UTC. Two further CMEs (SIDC CME 580 and 581) were observed to the north in SOHO/LASCO-C2 and to the east in STEREO-A/COR2 data on October 15, associated with an M1.9 flare (SIDC Flare 5731) and M1.2 flare (SIDC Flare 5740), respectively. These CMEs were mostly ahead of the Sun-Earth line but a glancing blow from a combination of these was predicted. Finally, a partial halo CME (SIDC CME 582) directed to the west was first detected in SOHO/LASCO-C2 data from 15:00 UTC on October 15 and was predicted to have a glancing blow arrival at Earth. Coronal Holes --------------------- An extended negative polarity equatorial coronal hole (combined SIDC Coronal Hole 126) began to transit the central meridian on October 16. Proton flux levels --------------------- The greater than 10 MeV proton flux was at background levels throughout the week. Electron fluxes at GEO --------------------- The greater than 2 MeV electron flux measured by GOES 19 and 18 was above the 1000 pfu threshold between October 13 and October 17, due to the influence of the high-speed stream at the start of the week. The 24-hour electron fluence was moderate levels at this time. The From October 18 the 2 MeV electron flux reduced and remained below the 1000pfu threshold for the rest of the week and the 24-hour electron fluence returned to nominal levels. Solar wind --------------------- On October 13 and 14, the Earth was under the influence of the high-speed stream associated with SIDC Coronal hole 116, which crossed the central meridian on October 08. The solar wind speed had a maximum of near 800 km/s on October 13. From October 15, the influence of the high-speed stream began to wane and by October 17 the solar wind speed was around 400 km/s. On October 17, the interplanetary magnetic field increased at around 06:00 UTC from 6 nt to 12 nT, likely due to the influence of a glancing glow from one of the CMEs from October 13. During this time, the solar wind speed remained around 400 km/s. Further transient features in the magnetic field were observed on October 18 and 19, which are likely the combined influence arrival of CMEs from October 13 and 15. The magnetic field strength reached a maximum of 21 nT at 08:20 UTC On October 18. Bz had a minimum vale of -12 nT at 09:31UTC on October 18. Bz was negative for a prolonged period between 15:15 UTC on October 18 and 03:00 on October 19 with values of around -8nT. Around this time, the solar wind speed gradually increased to values around 550 km/s where it remained till the end of the week, as the high-speed stream from SIDC Coronal hole 126 began to influence the Earth. Geomagnetism --------------------- Geomagnetic conditions reached active to minor storm conditions on October 13, due to the ongoing high-speed stream influence. Conditions reduced to mostly be at quiet to unsettled levels on October 15 to 17. From October 18, active to minor storm conditions were observed with one period of moderate storm levels globally (Kp 6), between 18:00 and 21:00 UTC on October 18, in response to the magnetic structures in the solar wind and the extended period of negative Bz, likely associated with the ICME arrivals. Locally, only minor storm conditions were observed (K bel 5). The geomagnetic conditions then reduced to unsettled conditions by the end of the week on October 19. --------------------------------------------------------------------------- DAILY INDICES DATE RC EISN 10CM Ak BKG M X 2025 Oct 13 132 128 141 021 C1.2 4 0 2025 Oct 14 172 128 154 008 C1.6 3 0 2025 Oct 15 /// 123 162 012 C1.6 5 0 2025 Oct 16 /// 136 161 004 C2.1 4 0 2025 Oct 17 131 117 164 009 C3.0 6 0 2025 Oct 18 /// 110 156 037 C2.3 5 0 2025 Oct 19 /// 112 149 020 C1.7 2 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 13 0512 0526 0539 N04E08 M1.9 SN 59/4248 III/2 13 0459 0526 0545 N22W17 M1.9 1 58/4246 III/2 13 0855 0919 0931 N22W17 M2.7 1F 58/4246 13 1304 1318 1339 N23W20 M1.2 1F 58/4246 II/2III/2 14 0035 0041 0044 N25W25 M2.0 SF 58/4246 14 1238 1247 1256 N06W07 M2.0 1 59/4248 14 2028 2036 2045 ////// M3.1 58/4246 15 0349 0415 0436 N24W41 M4.8 2 58/4246 CTM/1 15 0705 0718 0726 N24W41 M3.7 1N 58/4246 III/2 15 1401 1410 1441 ////// M1.1 58/4246 III/2 15 2155 2228 2305 ////// M2.7 58/4246 15 2337 2345 2352 N23W57 M2.4 S 58/4246 16 0017 0021 0024 N23W57 M1.1 S 58/4246 16 1353 1408 1422 N21W67 M1.3 SF 58/4246 16 1900 1916 1936 N22W68 M1.1 SF 58/4246 16 2312 2319 2328 N22W68 M1.0 SF 58/4246 17 0115 0128 0140 N24W66 M1.5 1F 58/4246 III/2 17 1227 1245 1301 ////// M1.1 58/4246 VI/2 17 1422 1432 1436 N22W75 M1.0 SF 58/4246 17 1614 1632 1647 ////// M1.3 58/4246 17 1647 1658 1708 ////// M1.2 58/4246 17 1855 1905 1912 N22W78 M1.1 S 58/4246 18 0023 0040 0049 ////// M1.0 58/4246 18 0226 0239 0247 ////// M1.1 58/4246 18 0632 0639 0644 ////// M1.2 58/4246 18 0649 0658 0704 ////// M1.3 58/4246 18 1037 1051 1059 ////// M1.5 58/4246 19 0146 0156 0204 ////// M1.0 58/4246 19 2003 2015 2026 ////// M1.8 58/4246 #--------------------------------------------------------------------# # 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 # #--------------------------------------------------------------------#