:Issued: 2025 Dec 08 2145 UTC :Product: documentation at http://www.sidc.be/products/bul #--------------------------------------------------------------------# # SIDC Weekly bulletin on Solar and Geomagnetic activity # #--------------------------------------------------------------------# WEEK 1301 from 2025 Dec 01 Solar Active Regions (ARs) and flares --------------- The solar flaring activity over the past week has reached high levels with background C-class flaring, 3 M-class flares and one 1 X-flare. A total of 14 active regions were numbered on the visible solar disk. The region responsible for the observed high levels of activity is SIDC Sunspot Group 687 (NOAA AR 4299, NOAA AR 4274), which was classified as magnetic type beta-gamma-delta for most of the week. It produced X1.9 flare (SIDC 6236) with peak time 02:49 UTC on Dec 01, an M1.1 flare (SIDC 6319) with peak time 19:21 UTC on Dec 06 and an M8.1 flare (SIDC 6318) with peak time 20:39 UTC on Dec 06. An M6.0 flare (SIDC 6285) with peak time at 02:50 UTC on Dec 04 was produced by SIDC Sunspot Group 714 (NOAA AR 4300), which was classified as magnetic type beta-delta that day. Other notable regions throughout the week are SIDC Sunspot Group 709/NOAA AR 4294, SIDC Sunspot Group 712/NOAA AR 4296, which have grown to be the largest regions on the visible solar disc and have both been classified as magnetic type beta-gamma-delta on multiple days. Regardless of their complexity these regions produced only low levels of activity. Coronal mass ejections --------------------- A few noteworthy coronal mass ejections (CMEs) were detected in the coronagraph imagery throughout the week. A fast partial halo CME with an estimated projected velocity of 850 km/s was detected in the LASCO/C2 coronagraph imagery starting at around 03 UTC on Dec 01. The CME was related to the X1.9 flaring activity produced by SIDC Sunspot Group 687 (NOAA AR 4274) at the north-east limb. The CME was directed off the Sun-Earth line and no notable impact on Earth was expected. A large filament eruption as visible in the SDO/AIA 30.4 nm imagery in the western solar hemisphere has lifting off the solar surface on the UTC morning of Dec 03, triggering a follow up eruption a few hours later. A combined slow CME was detected in the LASCO/C2 coronagraph imagery starting at 09:21 UTC on Dec 03 with estimated projected velocity below 400 km/s and a coronal dimming was observed around 10:30 UTC. Modelling results suggested that the CME would pass mostly off the Sun-Earth line and any possible minor glancing blow impacts on Dec 06, but might be mixed within the waning influence of an supposedly ongoing high speed stream. Another CME detected in the LASCO/C2 imagery starting at 06:36 UTC on Dec 04 following the C4.4 flaring with peak time 05:38 UTC produced by SIDC Sunspot Group 709 (NOAA Active Region 4294) and related to a coronal dimming first observed at 05:33 UTC was accompanied by a type IV radio burst registered at 08:32 UTC. The bulk of the CME was expected to miss the Earth with chances for a minor glancing blow mixed within the ambient fast solar wind late on Dec 06 or Dec 07. A halo CME (SIDC CME 605) was first detected in the LASCO/C2 imagery starting at 19:24 UTC on Dec 06 and visible to the north-east in STEREO at 20:38 UTC. The CME is associated to the M1.1-flaring from SIDC Sunspot Group 687 (NOAA Active Regions 4274, 4299). A consequent faster halo CME was observed after related to the M8.1 flare from the same region. Associated type II and type IV radio emissions were registered at 20:40 UTC and 20:57 UTC on Dec 06, and a large coronal dimming with post-eruptive arcade was detected in the SDO/AIA imagery as well. The CME was estimated to have a 3D velocity of 850 km/s with an estimated arrival time early UTC on Dec 09. Coronal Holes --------------------- Two negative polarity coronal holes (SIDC Coronal Holes 140 and 141) were present on the visible disc during the past week. SIDC Coronal Hole 140 was a larger equatorial coronal hole, extending to mid-latitudes to the north. It crossed the central meridian on Nov 30 and an associated high-speed stream emanating from it was expected to arrive at Earth on Dec 03. Proton flux levels --------------------- The greater than 10 MeV GOES proton flux was at nominal levels throughout the entire week with mild enhancements (below 10 pfu radiation storm thresholds) registered on Dec 06 following the M8.1 flaring and related halo CME. Electron fluxes at GEO --------------------- The greater than 2 MeV electron flux as measured by GOES 18 and GOES 19 was exceeding the 1000 pfu threshold for prolonged periods of time on multiple days during the week. The corresponding electron fluence was at moderate levels for most of the week. Solar wind --------------------- The solar wind conditions (as measured by ACE) reflected an anticipated high speed stream (HSS) arrival with a co-rotating interaction region (CIR) detected in the UTC afternoon on Dec 03. The HSS is associated with the recurrent SIDC Coronal Hole 140 (negative polarity), which crossed the central meridian on Nov 30. Related to the CIR/HSS arrival the magnitude of the interplanetary magnetic field (B) reached a maximum value of 22.7 nT on Dec 04, with a minimum Bz of -15.3 nT. The B field phi angle was predominantly in the negative sector (directed towards the Sun) reflecting the polarity of the geo-effective coronal hole (SIDC Coronal Hole 140). The solar wind speed reached a maximum of 771 km/s and remained at high values until the UTC afternoon on Dec 07, when it started to decline towards background slow solar wind conditions. Geomagnetism --------------------- The geomagnetic conditions at the beginning of the week started at quiet to active levels and were predominantly quiet to unsettled on Dec 02. Minor storm levels and an isolated period of major geomagnetic storm were registered on Dec 03 (with NOAA Kp reaching 6.67 between 18:00 to 21:00 UTC) as a consequence of an expected high speed stream arrival. Further minor storm levels were detected on Dec 04. The corresponding geomagnetic conditions locally over Belgium have registered moderate storm levels between 19:00 and 23:00 UTC on Dec 03 and up to active levels there after. Quiet to active geomagnetic conditions we observed from Dec 05 onwards. --------------------------------------------------------------------------- DAILY INDICES DATE RC EISN 10CM Ak BKG M X 2025 Dec 01 184 153 200 012 C1.6 0 1 2025 Dec 02 217 169 200 013 C1.6 0 0 2025 Dec 03 /// 173 209 036 C1.6 0 0 2025 Dec 04 /// 181 220 028 C1.8 1 0 2025 Dec 05 223 166 206 016 C1.6 0 0 2025 Dec 06 /// 160 200 014 C1.2 2 0 2025 Dec 07 /// 161 194 007 C1.7 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 01 0227 0249 0305 N20E81 X1.9 1N ///4299 II/2/3I/3 9V/3 04 0236 0250 0259 N06E54 M6.0 1F 26/4300 II/2 06 1858 1921 1936 N23E08 M1.1 1F 24/4299 VI/1 06 2029 2039 2049 N21E04 M8.1 2 24/4299 V/3II/3 07 2356 0012 0023 ////// M2.4 24/4299 #--------------------------------------------------------------------# # 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 # #--------------------------------------------------------------------#