:Issued: 2026 Apr 13 2151 UTC :Product: documentation at http://www.sidc.be/products/bul #--------------------------------------------------------------------# # SIDC Weekly bulletin on Solar and Geomagnetic activity # #--------------------------------------------------------------------# WEEK 1319 from 2026 Apr 06 Solar Active Regions (ARs) and flares --------------- Solar flaring activity was low for most of the week and reached moderate levels briefly on 9 April. One M-class flare and twenty-five C-class flares were recorded during the week. In total, eighteen active regions were observed on the visible solar disc over the course of the week. The largest flare was an M1.0 flare (SIDC Flare 7388), peaking at 08:45 UTC on 9 April, associated with SIDC Sunspot Group 838 (NOAA AR 4409). This region was the main driver of the flaring activity at the beginning of the week, together with SIDC Sunspot Group 842 (NOAA AR 4414). Towards the end of the week, the newly emerged SIDC Sunspot Group 845 (NOAA AR 4417) also contributed to low-level flaring activity. Coronal mass ejections --------------------- No Earth-directed coronal mass ejections (CMEs) were detected in the available coronagraph imagery over the past week. Coronal Holes --------------------- A recurrent positive polarity coronal hole (SIDC Coronal Hole 154) began crossing the central meridian on 7 April. A mid-latitude positive polarity coronal hole in the southern hemisphere (SIDC Coronal Hole 159) started crossing the central meridian late on 11 April. Proton flux levels --------------------- The greater than 10 MeV proton flux, as measured by GOES-18, remained below the 10 pfu threshold throughout the week. Electron fluxes at GEO --------------------- The greater than 2 MeV electron flux, as measured by GOES-19, exceeded the 1000 pfu alert threshold during the first part of the week, with peak values above 10,000 pfu on April 9, before decreasing to mostly below threshold levels toward the end of the week. The 24-hour electron fluence was at moderate to high levels early in the week and decreased to normal to moderate levels by the end of the period. Solar wind --------------------- Solar wind conditions at the beginning of the week reflected the waning influence of a high-speed stream from SIDC Coronal Hole 149, with solar wind speeds between 500 and 570 km/s on 6 April. From 7 to 9 April, solar wind parameters gradually returned to a slow solar wind regime, with speeds decreasing to around 350 km/s and the interplanetary magnetic field remaining weak, below 6 nT. From late on 9 April, solar wind conditions became slightly enhanced again with the arrival of a compression region, followed by a high-speed stream associated with a recurrent positive polarity coronal hole. The solar wind speed increased from about 380 km/s to around 700 km/s by 11 April, while the interplanetary magnetic field reached up to 14 nT and the Bz component fluctuated between -8 nT and +12 nT. By 12 April, the high-speed stream influence was waning, with the solar wind speed decreasing to around 500 km/s. Geomagnetism --------------------- Geomagnetic conditions were mostly quiet to unsettled at the beginning of the week. From 00:00 UTC on 10 April through the first half of 11 April, geomagnetic activity increased under the influence of a high-speed stream associated with positive polarity SIDC Coronal Hole 154. During this period, active conditions were observed both globally (NOAA Kp = 4 to 4+) and locally over Belgium (K-Bel = 4). For the remainder of the week, geomagnetic conditions were at quiet to unsettled levels (Kp 1 to 3; K-Bel 1 to 3), as the influence of the high-speed stream waned. --------------------------------------------------------------------------- DAILY INDICES DATE RC EISN 10CM Ak BKG M X 2026 Apr 06 /// 107 116 010 B4.7 0 0 2026 Apr 07 098 097 109 010 B4.8 0 0 2026 Apr 08 079 079 108 008 B6.4 0 0 2026 Apr 09 080 066 098 006 B3.9 1 0 2026 Apr 10 023 031 094 020 B3.1 0 0 2026 Apr 11 /// 045 093 013 B2.0 0 0 2026 Apr 12 /// 043 099 009 B2.2 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 09 0823 0845 0905 N02W77 M1.0 SF 73/4409 #--------------------------------------------------------------------# # 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 # #--------------------------------------------------------------------#