:Issued: 2026 Apr 28 1235 UTC :Product: documentation at http://www.sidc.be/products/meu #--------------------------------------------------------------------# # DAILY BULLETIN ON SOLAR AND GEOMAGNETIC ACTIVITY from the SIDC # # (RWC Belgium) # #--------------------------------------------------------------------# SIDC URSIGRAM 60428 SIDC SOLAR BULLETIN 28 Apr 2026, 1234UT SIDC FORECAST SOLAR FLARES : M-class flares expected (probability >=50%) GEOMAGNETISM : Minor storm expected (A>=30 or K=5) SOLAR PROTONS : Quiet PREDICTIONS FOR 28 Apr 2026 10CM FLUX: 140 / AP: 007 PREDICTIONS FOR 29 Apr 2026 10CM FLUX: 135 / AP: 031 PREDICTIONS FOR 30 Apr 2026 10CM FLUX: 130 / AP: 029 Solar Active Regions and flaring: Solar flaring activity was low over the past 24 hours, with only C-class flares identified. The largest flare was a C9.0 flare (SIDC Flare 7541) peaking on Apr 28 at 09:23 UTC, which was produced by SIDC Sunspot Group 847 (NOAA Active Region 4420). During the flare, the source region (SIDC Sunspot Group 847) of the flare had beta- gamma-delta configuration of its photospheric magnetic field. A total of 7 numbered sunspot groups were identified on the disk over the past 24 hours. SIDC Sunspot Groups 805 and 847 (NOAA AR 4425 and 4420) are the most complex regions with their beta-gamma-delta magnetic configuration. Solar flaring activity is expected to be low to moderate over the next 24 hours, with few C-class flares, possibly M-class flares and a low chance for X-class flares. Coronal mass ejections: No Earth-directed coronal mass ejections (CMEs) were detected in the available coronagraph observations during the last 24 hour. Coronal holes: SIDC Coronal Hole (CH) 149, spanning 8 S - 25 S (negative polarity), has crossed the central meridian, and the high-speed streams from this CH may enhance the solar wind environment near Earth during Apr 29 - May 01. Solar wind: Solar wind conditions have transitioned to slow solar wind regime. The solar wind speed ranged between 355 km/s and 480 km/s. The North-South component (Bz) ranged between -3 and 4 nT. The interplanetary magnetic field ranged from 2 nT to 5 nT. Slow solar wind conditions are expected to continue over the next 24 hours unless the high speed streams from the SIDC Coronal Hole 149, which crossed the central meridian during Apr 26-28 (negative polarity), arrives at Earth. Geomagnetism: Geomagnetic conditions were globally and locally quiet (NOAA Kp and K BEL 1 to 2). In the next 24 hours, active to minor storm conditions (K 4 to 5) are possible if the high speed streams from the SIDC Coronal Hole 149, which crossed the central meridian during Apr 26-28 (negative polarity), arrives at Earth. Proton flux levels: The greater than 10 MeV GOES proton flux was below the threshold level over the past 24 hours and it is expected to remain so for the next 24 hours. Electron fluxes at GEO: The greater than 2 MeV electron flux, as measured by GOES-19 and GOES-18 satellites, remained below the threshold level over the past 24 hours and is expected to remain so in the coming 24 hours. The 24h electron fluence is presently at normal level and is expected to be at normal to moderate levels in the next 24 hours. TODAY'S ESTIMATED ISN : 137, BASED ON 18 STATIONS. SOLAR INDICES FOR 27 Apr 2026 WOLF NUMBER CATANIA : 148 10CM SOLAR FLUX : 142 AK CHAMBON LA FORET : 007 AK WINGST : 007 ESTIMATED AP : 007 ESTIMATED ISN : 134, BASED ON 30 STATIONS. NOTICEABLE EVENTS SUMMARY DAY BEGIN MAX END LOC XRAY OP 10CM Catania/NOAA RADIO_BURST_TYPES NONE END BT #--------------------------------------------------------------------# # 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 # #--------------------------------------------------------------------#