:Issued: 2026 Mar 31 1744 UTC :Product: documentation at http://www.sidc.be/products/bul #--------------------------------------------------------------------# # SIDC Weekly bulletin on Solar and Geomagnetic activity # #--------------------------------------------------------------------# WEEK 1317 from 2026 Mar 23 Solar Active Regions (ARs) and flares --------------- The solar flaring activity of the past week reach moderate levels on 26 and 28 Mar and low levels the rest of the week. The first M-class flare of the week (SIDC flare 7259) was an M3.9 that peaked on 26 Mar at 06:23 UTC and was emitted by SIDC Sunspot Group (SG) 832 (NOAA Active Region [AR] 4403, Alpha magnetic configuration). The second flare (SIDC flare 7282) was an M1.3 that peaked on 28 Mar at 04:14 UTC and was produced by SIDC SG 836 (NOAA AR 4405, Beta magnetic configuration). Coronal mass ejections --------------------- A Coronal Mass Ejection (CME) seen in LASCO-C2 images as launched on 22 Mar at 16:00 UTC was caused by a complex filament eruption. Although it did not create a partial halo CME, its northern component delivered a glancing blow at Earth on 25 Mar at 05:55 UTC. Coronal Holes --------------------- SIDC Coronal Hole (CH) 156 (equatorial coronal hole with a positive polarity) started crossing the solar meridian on 25 Mar. Although it did not produce a geo-effective High Speed Stream (HSS), unusually low densities were observed on 28 Mar. SIDC CH 153 (at the solar south pole with positive polarity) started crossing the solar meridian on 26 Mar. It also does not appear to cause a geo-effective HSS, it might have caused the increased the solar wind speed on 29 Mar. Proton flux levels --------------------- The greater than 10 MeV proton flux, as measured by the GOES-19 satellite, was at nominal levels during the past week. Electron fluxes at GEO --------------------- The greater than 2 MeV electron flux, as measured by GOES-19, was above the 1000 pfu alert threshold for almost the entire past week. It reached a peak value of 13 kpfu on 27 Mar at 05:25 UTC. Solar wind --------------------- At the start of the previous week the Solar Wind (SW) conditions were affected by an HSS that lasted until the second half of 24 Mar. The SW speed reached 700 km/s, the interplanetary magnetic field (B) dropped 13 nT, and its North-South component (Bz) registered values as low as -12 nT. On 25 Mar at 05:55 UTC a glancing blow from a CME launched on 22 Mar at 16:00 UTC affected the SW conditions. The SW speed increased from 500 to 630 km/s, B increased to 10 nT, and Bz varied from -8 nT to 8 nT. This effect lasted approximately 16 hours and the SW conditions returned to a slow SW regime until the end of 28 Mar. During that calm period the SW speed varied between 600 and 350 km/s, B ranged between 1 and 8 nT, and Bz between -5 and 7 nT. A transient event, probably a combination of enhanced SW speed associated with the crossing of the central meridian of CH 153 and a sector boundary crossing, affected Earth at the very early hours of 29 Mar. The SW speed increased to 450 km/s, B increased to 13 nT, and Bz ranged between -8 and 12 nT. Geomagnetism --------------------- The global geomagnetic conditions reached minor storm levels on 23 Mar (NOAA Kp 5 at 15:00 - 18:00 UTC and 5- at 12:00 - 15:00 UTC) and on 25 Mar (NOAA Kp 5+ at 06:00 - 09:00 UTC) as a result of the HSS that was present at the beginning of last weak. They then decreased to quiet to unsettled levels (NOAA Kp 1+ tp 3+), until the arrival of the transient event on 29 Mar. The later caused a temporary increase to active levels (NOAA Kp 4- 00:00-06:00 UTC). The local geomagnetic conditions registered a minor storm on 23 Mar (K BEL 5 at 15:00 - 21:00 UTC) and short intervals of active levels (K BEL 4) on 25, 28, and 29 Mar. The rest of the past week they ranged between quiet and unsettled levels (K BEL 1 to 3). --------------------------------------------------------------------------- DAILY INDICES DATE RC EISN 10CM Ak BKG M X 2026 Mar 23 /// 116 124 040 B6.8 0 0 2026 Mar 24 139 116 128 017 B5.9 0 0 2026 Mar 25 123 113 140 013 B8.3 0 0 2026 Mar 26 173 125 152 010 C1.0 1 0 2026 Mar 27 170 144 156 008 C1.1 0 0 2026 Mar 28 /// 139 162 012 C1.0 1 0 2026 Mar 29 /// 142 158 014 B8.4 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 26 0611 0623 0631 N13E59 M3.9 1N 64/4403 III/2II/2 28 0216 0416 0535 ////// M1.3 68/4405 #--------------------------------------------------------------------# # 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 # #--------------------------------------------------------------------#