SIDC Weekly Bulletin
Review of past solar and geomagnetic activity.| Source | SIDC (RWC-Belgium) |
| Frequency | Weekly |
| Format | Plain text |
| Mail header | SIDC Weekly Bulletin |
| SIDC code | bul |
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:Issued: 2025 Apr 21 1221 UTC :Product: documentation at http://www.sidc.be/products/bul #--------------------------------------------------------------------# # SIDC Weekly bulletin on Solar and Geomagnetic activity # #--------------------------------------------------------------------# WEEK 1268 from 2025 Apr 14 Solar Active Regions (ARs) and flares --------------- Solar flaring activity was high in the beginning of the week, with five M-class flares recorded on April 13-14 and moderate to low for the rest of the week. In total, eight M-class flares were recorded. The strongest flares were an M4.2 flare (SIDC Flare 4126) peaking at 06:50 UTC on April 14, associated with SIDC Sunspot Group 469 (NOAA Active Region 4055) and an M4.4 flare (SIDC Flare 4156) from beyond the east limb, peaking at 23:50 UTC on April 18. There was a total of eleven active regions on the visible disk during the week. The most complex one at the beginning of the week was SIDC Sunspot Group 469 (NOAA Active Region 4055, magnetic type beta-gamma-delta). Later during the week, SIDC Sunspot Groups 450, 473 and 474 (NOAA Active Regions 4060, 4062 and 4064) evolved to magnetic type beta-gamma during different periods of the week, with SIDC Sunspot Group 450 having a magnetic type beta-delta on April 18. Coronal mass ejections --------------------- Few Coronal Mass Ejections (CMEs) were detected during the week, but were either events near the west or east limb or backsided and had no impact on Earth. The most important one was a wide CME observed in LASCO/C2 and LASCO/C3 coronagraph imagery, lifting off around 00:00 UTC on April 19. It was most likely associated with the M4.4 flare (SIDC Flare 4156) that peaked at 23:50 UTC on April 18. A few filament eruptions were observed in SDO/AIA 304 data during the week, but either no associated CME was observed in the available coronagraph imagery, or it was not Earth-directed. Coronal Holes --------------------- Three coronal holes have crossed the central meridian during the last week. The first (SIDC Coronal Hole 105) was an equatorial, negative polarity coronal hole that crossed the central meridian on April 15. The second was a southern, mid-latitude, negative polarity coronal hole (SIDC Coronal Hole 104) that started to cross the central meridian on April 17. The third was an equatorial, positive polarity coronal hole (returning SIDC Coronal Hole 82) that crossed the central meridian on April 19. Proton flux levels --------------------- The greater than 10 MeV proton flux was below the 10 pfu threshold throughout the week. Electron fluxes at GEO --------------------- The greater than 2 MeV electron flux as measured by GOES 16 and GOES 18 was above the threshold at different times during the week, following a diurnal variation. The 24-hour electron fluence was at nominal levels throughout the week. Solar wind --------------------- The solar wind conditions were enhanced at the beginning of the week, under the waning influence of a high-speed stream from the elongated, negative polarity coronal hole (SIDC Coronal Hole 87) that first crossed the central meridian on April 07. A shock was detected in the solar wind data (DSCOVR) at 16:35 UTC on April 15. The interplanetary magnetic field jumped from 6 nT to 17 nT and briefly reached values up to 23 nT. The Bz component jumped from -4 nT to -11 nT. The solar wind speed jumped from 400 km/s to around 480 km/s and then increased up to 515 km/s. The solar wind density at the shock jumped from 5.6 ppcc to around 24.4 ppcc. The shock was most likely related to the expected interplanetary Coronal Mass Ejection (ICME) arrivals, associated with the CMEs that lifted off around 23:00 UTC on April 12 and the partial halo CME that lifted off around 08:30 UTC on April 13. A gradual return to the slow solar wind regime followed. The solar wind conditions (ACE and DSCOVR) were enhanced again on April 20, likely due to the arrival of a high-speed stream from the southern, positive polarity coronal hole (SIDC Coronal Hole 104). Geomagnetism --------------------- Geomagnetic conditions globally reached severe storm levels (NOAA Kp 8- ) in the UTC evening of April 16. Geomagnetic conditions locally reached moderate storm levels (K BEL 6) during the same period. The geomagnetic storms were most likely the result of the arrivals of the interplanetary Coronal Mass Ejections (ICMEs), associated with the CMEs that lifted off around 23:00 UTC on April 12 and the partial halo CME that lifted off around 08:30 UTC on April 13. Mostly unsettled to active levels, with isolated minor storm intervals (NOAA Kp 3 to 5, K BEL 3 to 5) were observed during the rest of the week. --------------------------------------------------------------------------- DAILY INDICES DATE RC EISN 10CM Ak BKG M X 2025 Apr 14 /// 080 152 025 C1.8 2 0 2025 Apr 15 /// 069 153 030 C1.4 2 0 2025 Apr 16 /// 089 148 067 C1.0 0 0 2025 Apr 17 /// 100 151 011 B8.7 0 0 2025 Apr 18 142 115 156 018 C1.0 1 0 2025 Apr 19 /// 112 157 022 C1.0 0 0 2025 Apr 20 /// 125 156 014 C1.0 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 14 0600 0605 0611 ////// M1.4 26/4055 14 0636 0650 0658 N06W82 M4.2 SF 26/4055 15 1004 1020 1028 ////// M1.5 /////// 15 1757 1813 1827 ////// M1.3 /////// 18 2308 2350 0015 ////// M4.4 /////// II/1 20 1137 1211 1259 ////// M1.0 ///4068 #--------------------------------------------------------------------# # 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 # #--------------------------------------------------------------------#
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This report is sent once a week, typically on a monday.The weekly bulletin gives an overview of solar and geomagnetic activity of the past week and includes a noticeable solar events list.
Check the ISES code book for information on ISES codes.