:Issued: 2026 Mar 18 1236 UTC :Product: documentation at http://www.sidc.be/products/meu #--------------------------------------------------------------------# # DAILY BULLETIN ON SOLAR AND GEOMAGNETIC ACTIVITY from the SIDC # # (RWC Belgium) # #--------------------------------------------------------------------# SIDC URSIGRAM 60318 SIDC SOLAR BULLETIN 18 Mar 2026, 1235UT SIDC FORECAST SOLAR FLARES : C-class flares expected, (probability >=50%) GEOMAGNETISM : Quiet (A<20 and K<4) SOLAR PROTONS : Quiet PREDICTIONS FOR 18 Mar 2026 10CM FLUX: 113 / AP: 010 PREDICTIONS FOR 19 Mar 2026 10CM FLUX: 115 / AP: 024 PREDICTIONS FOR 20 Mar 2026 10CM FLUX: 117 / AP: 041 Solar Active Regions and flaring: Solar flaring activity was moderate over the past 24 hours. The largest flare was an M2.7 flare (SIDC Flare 7228) peaking on March 18 at 08:42 UTC, which was produced by SIDC Sunspot Group 820 (NOAA Active Region 4392). This region is the largest on disk, with Beta-Gamma magnetic configuration. There are currently 5 numbered regions on the disk. SIDC Sunspot Group 824 emerged in the southeast quadrant and was numbered over the period. Sunspot Group 823 (NOAA Active Region 4396) decayed to a plage region. SIDC Sunspot Group 819 (NOAA Active Region 4393) also produced C-class flaring activity while the other regions are simple and were mostly quiet. Solar flaring activity is expected to be low over the next 24 hours, with C-class flares expected and further isolated M-class flares possible. Coronal mass ejections: The filament eruption reported yesterday, originating from around S05W10, is visible as a faint Coronal Mass Ejection (CME) E in STEREO-A COR-2 coronagraph data and may have a glancing blow at Earth from late on March 20. The M2.7 flare (SIDC Flare 7228) was also associated with a large dimming, EUV wave and Type II radio burst. An associated CME was observed in STEREO A COR2 at 09:23 UTC on March 18 and to the west in SOHO/LASCO-C2 data rom 10:36 UTC on March 18, after a data gap. Analysis of this CME is ongoing. Coronal holes: The southern midlatitude extension of the large positive polarity coronal hole (SIDC Coronal Hole 154) continues to cross the central meridian. A northern midlatitude extension to a large negative polarity Coronal hole (SIDC Coronal Hole 147) has also begun to transit the central meridian. Solar wind: Over the past 24 hours, the solar wind parameters gradually returned to slow solar wind conditions. The solar wind speed decreased from 500 kms to around 400 km/s. The total magnetic field was stable around 5 nT. Bz had a minimum of -4 nT. The interplanetary magnetic field phi angle was mostly in the positive sector (directed towards the Sun). Slow solar wind conditions are expected for March 18 and enhanced conditions are expected from late on March 19 due to an anticipated CME arrival (SIDC CME 639) combined with a possible sector boundary crossing. Geomagnetism: Over the past 24 hours, the geomagnetic conditions were at quiet levels globally and locally (NOAA KP 3 and K BEL 3). Quiet conditions are expected on March 18 and Minor to moderate storm conditions are possible from late on March 19 due to the possible ICME arrival and influence from the sector boundary crossing. Proton flux levels: The greater than 10 MeV proton flux was below the 10 pfu threshold over the past 24 hours. It is expected to remain below this threshold level over the next 24 hours. Electron fluxes at GEO: The greater than 2 MeV electron flux, as measured by GOES-18 and GOES-19 satellites, exceeded the 1000 pfu threshold and reached a maximum of 2232 pfu. The greater than 2 MeV electron flux is expected to again exceed the 1000 pfu threshold over the next 24 hours. The electron fluence was at moderate levels and is expected to be at moderate levels for the next 24 hours. TODAY'S ESTIMATED ISN : 068, BASED ON 22 STATIONS. SOLAR INDICES FOR 17 Mar 2026 WOLF NUMBER CATANIA : /// 10CM SOLAR FLUX : 111 AK CHAMBON LA FORET : 007 AK WINGST : 004 ESTIMATED AP : 003 ESTIMATED ISN : 066, BASED ON 21 STATIONS. NOTICEABLE EVENTS SUMMARY DAY BEGIN MAX END LOC XRAY OP 10CM Catania/NOAA RADIO_BURST_TYPES 18 0826 0842 0857 ////// M2.7 54/4392 III/2 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 # #--------------------------------------------------------------------#