Solar Activity Alerts

:Product: Forecast Discussion :Issued: 2026 Sep 15 1230 UTC # Prepared by the U.S. Dept. of Commerce, NOAA, Space Weather Prediction Center # Solar Activity .24 hr Summary... Solar activity continued at very low levels with occasional B-class flaring. There are four numbered sunspot regions on the visible disk. All but Region 4531 (S08W02, Bxo/beta), which was numbered this period, are stable unipolar groups. No Earth-directed CMEs were observed in available coronagraph imagery. .Forecast... Solar activity is expected to remain at very low levels, with a decreasing chance for isolated C-class flares and a slight chance for M-class flares through 17 Sep. Energetic Particle .24 hr Summary... The greater than 2 MeV electron flux was at high to moderate levels, with a peak flux of 4,650 pfu observed at 14/1315 UTC. The greater than 10 MeV proton flux has declined but remains slightly elevated following a peak of 4 pfu observed at 14/1520 UTC. .Forecast... The greater than 2 MeV electron flux is expected to continue at high levels through 17 Sep. The greater than 10 MeV proton flux is anticipated to undergo a slow decline toward background levels through 17 Sep. Solar Wind .24 hr Summary... Solar wind parameters were slightly enhanced throughout the period, consistent with transient passage and the likely onset of a negative polarity coronal hole high-speed stream (-CH HSS). Total field strength (Bt) gradually rose to a peak of 14 nT after 14/1800 UTC before reaching as high as 16 nT late in the period. The North-South (Bz) component was variable in the first half of the period and reached a maximum southward deflection of -9 nT before turning and remaining northward after 14/2230 UTC. Solar wind speeds held relatively slow between 350 and 380 km/s before climbing sharply after 15/1114 UTC to over 600 km/s. This wind speed increase was a notable sharp rise in temperature. The phi angle shifted into a predominantly negative (towards the Sun) early in the period. .Forecast... Negative polarity CH HSS effects are anticipated to persist through 17 Sep. Additional enhancements are likely on 16 and 17 Sep due to flanking influences from CMEs that departed the Sun on 13 and 14 Sep. Geospace .24 hr Summary... The geomagnetic field was at quiet to active levels in response to transient influences. .Forecast... Geomagnetic activity is expected to reach active to G1 (Minor) storm levels on 15 and 16 Sep, with G1 conditions remaining possible on 17 Sep due to combined CH and CME effects.