:Issued: 2025 Mar 24 1631 UTC :Product: documentation at http://www.sidc.be/products/bul #--------------------------------------------------------------------# # SIDC Weekly bulletin on Solar and Geomagnetic activity # #--------------------------------------------------------------------# WEEK 1264 from 2025 Mar 17 Solar Active Regions (ARs) and flares --------------- Solar flaring activity was at low to moderate levels over the week. There was a total of 24 numbered active regions observed on the solar disk over the week. There were three isolated M-class flares recorded. The largest was an M1.5 flare (SIDC Flare 3879) peaking on March 19 at 20:40 UTC, which was produced by SIDC Sunspot Group 440 (NOAA Active Region 4031). The other M-class flares were an M1.0 flare (SIDC Flare 3870) peaking on March 17 at 19:33 UTC, which was associated with a filament eruption near SIDC Sunspot Group 445 (NOAA Active Region 4033), and an M1.2 flare (SIDC Flare 3887) peaking on March 21 at 15:58 UTC, which was associated with SIDC Sunspot Group 405 (NOAA Active Region 4028). At then end of the week the largest and most complex region on disk (with Beta-Gamma magnetic configuration) was SIDC Sunspot Group 450 (NOAA Active Region 4036). The other regions on the disk at the end of the week were simple and quiet. Coronal mass ejections --------------------- Three possible Earth-directed Coronal Mass Ejections (CMEs) were detected in the available coronagraph imagery over the past week. A partial halo CME that was observed on March 16, associated with on disk signature in the north-east of the solar disk. A filament eruption was observed in the north-west quadrant on March 17 around 10:30 UTC with a CME seen in SOHO/LASCO-C2 data from 11:24 UTC. Thirdly, a faint partial halo CME to the south-east detected on March 21 16:00 UTC. This CME appears to originate from a dimming that occurred near the central meridian around 15:45 UTC March 21. Coronal Holes --------------------- A small negative polarity equatorial coronal hole (SIDC Coronal Hole 93) began to cross the central meridian on March 19. At the end of the week SIDC Coronal Hole 60 (a mid-latitude coronal hole with a positive polarity) began to traverse the central meridian on March 23. Proton flux levels --------------------- The greater than 10 MeV proton flux as measured by GOES-18 was below the 10pfu threshold. Electron fluxes at GEO --------------------- The greater than 2 MeV electron flux was above the 1000 pfu threshold between March 16 and March 19, before reducing, and remained below the threshold for the remainder of the week. The 24h electron fluence was at moderate levels until March 19 and then was at nominal levels. Solar wind --------------------- The solar wind conditions reflected a slow solar wind regime at the start of the week. From 14:00 UTC on March 18, the solar wind parameters showed an enhancement in the magnetic field and solar wind speed, with values reaching near 600 km/s. This was likely a combination of high-speed steam effects and a glancing blow from a CME. The solar wind speed and magnetic field then gradually decreased on March 20 before increasing again when a shock was observed around 01:40 UTC on March 21. At this time, the total interplanetary magnetic increased from 3 nT to 6 nT, with the Bz component reaching a minimum of -6 nT. The solar wind speed jumped from 388 km/s to 440 km/s. The interplanetary magnetic field strength increased further reaching a maximum value of 39 nT at 17:43 UTC March 21. The Bz reached a minimum value of -22nT and was consistently negative for a sustained period between 22:30 UTC March 21 and 02:30 UTC March 22. The solar wind speed gradually increased during this time from 380 km/s to a maximum of around 550 km/s on March 22 around 21:00 UTC. From 23 March, the CME influence began to wane and the solar wind speed decreased to below 400 km/s, while the magnetic field stabilised around 6nT. Geomagnetism --------------------- Geomagnetic conditions were mostly quiet to unsettled on March 16 to 18. On March 19 the conditions were active with one period of minor storm conditions. Moderate storm conditions (NOAA Kp 6-) were reached between 00:00 and 03:00 UTC on March 22. This was due to the ICME arrival and extended period of strong negative Bz. On March 23, the geomagnetic conditions reduced and were at unsettled to active conditions. --------------------------------------------------------------------------- DAILY INDICES DATE RC EISN 10CM Ak BKG M X 2025 Mar 17 214 204 204 016 C1.2 1 0 2025 Mar 18 /// 193 184 013 C1.1 0 0 2025 Mar 19 /// 165 180 018 C1.2 1 0 2025 Mar 20 132 163 170 008 C1.2 0 0 2025 Mar 21 206 162 178 023 C1.6 1 0 2025 Mar 22 /// 179 178 029 C1.6 0 0 2025 Mar 23 /// 135 168 011 C1.3 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 17 1925 1933 1940 ////// M1.0 95/4033 19 2021 2040 2047 N14W36 M1.5 1N 94/4031 21 1534 1558 1623 S19W31 M1.2 1N 91/4028 TM/1I/1I/1 3 #--------------------------------------------------------------------# # 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 # #--------------------------------------------------------------------#