Routine Space Environment Product (Daily)
Issued by NWS
Issued by NWS
410 FXXX12 KWNP 180031 DAYDIS :Product: Forecast Discussion :Issued: 2026 May 18 0030 UTC # Prepared by the US Dept. of Commerce, NOAA, Space Weather Prediction Center # Product description and SWPC contact on the Web # http://www.swpc.noaa.gov/wwire.html # # Forecast Discussion # Solar Activity .24 hr Summary... Solar activity was at moderate levels due to an M1.4 flare at 17/0339 UTC that originated from just beyond the northwest limb. Region 4436 (N19W39, Dso/beta) continued to exhibit decay and produced a C9.7 flare at 17/2053 UTC with an associated 10.7 cm radio burst of 370 sfu. Region 4441 (N18E14, Dao/beta) underwent evolution as it gained penumbra on both poles and began to show signs of mixed polarity in its intermediate portion. Regions 4442 (S16E44, Cro/beta) and 4443 (S15E60, Bxo/beta) emerged, were numbered this period, but were otherwise relatively quiet. No Earth-directed CMEs were observed in available coronagraph imagery. .Forecast... Solar activity is likely to be at low levels, with a chance for additional M-class (R1-R2/Minor-Moderate) flares through 20 May. Energetic Particle .24 hr Summary... The greater than 2 MeV electron flux increased to high levels with a peak flux of 6,120 pfu occurring at 17/1740 UTC. The greater than 10 MeV proton flux was at background levels, though beginning to show contamination signatures from the elevated electron flux. .Forecast... The greater than 2 MeV electron flux is expected to remain at moderate to high levels through 18 May before possibly returning to normal to moderate levels by late on 19 May with any CME glancing effects from the 16 May event. If this occurs, then electron flux in geostationary orbit will likely remain at normal to moderate levels on 20 May. The greater than 10 MeV proton flux is expected to stay at background levels through 20 May. Solar Wind .24 hr Summary... The solar wind parameters reflected continued influence of a negative polarity coronal hole. Total field averaged under 5 nT and the Bz component of the IMF was near neutral. Solar wind speeds gradually decreased from speeds between 600-650 km/s to approximately 550 km/s by the end of the period. The phi angle was largely negative with two hour-long periods of positive orientation. .Forecast... A negative polarity CH HSS regime is expected to continue to slowly diminish through 20 May. Additional enhancements are possible on 18 and 19 May due to aforementioned glancing CME influences from the 16 May event. Geospace .24 hr Summary... The geomagnetic field was at quiet levels. .Forecast... G1 (Minor) geomagnetic storming periods, with a chance for G2 (Moderate) levels, are likely on 18-19 May due to any glancing CME effects from the 16 May event as modeling efforts suggest that a bulk of the material should pass just north of Earth. Quiet to unsettled conditions are expected on 20 May as negative polarity CH HSS effects come to a close.