Date: 2025 Dec 17 0030 UTC
Prepared by the U.S. Dept. of Commerce, NOAA, Space Weather Prediction Center
Solar activity was at low levels. Only low level C-class flares were observed. Slight growth was observed in Regions 4310 (N01W38, Bxi/beta) and new Region 4311 (N03E16, Cro/beta). The rest of the spotted regions were either stable or in decay. No Earth-directed CMEs were observed.
Forecast: Solar activity is expected to be low with a slight chance for M-class flares (R1-R2, Minor-Moderate) on 17-19 Dec.Energetic Particle The greater than 2 MeV electron flux briefly reached high levels with a peak flux of 1,020 pfu observed at 16/0340 UTC. The greater than 10 MeV proton flux remained steady at background levels during the period.
Forecast: The greater than 2 MeV electron flux is expected to remain at normal to moderate levels through 18 Dec with a chance for high levels on 19 Dec due to HSS influences. The greater than 10 MeV proton flux is expected to persist at background levels over 17-19 Dec.
Solar wind parameters were under the influence of a negative polarity CH HSS. Solar wind speed increased from approximately 500 km/s to between 550-700 km/s. Total field decreased from 14 nT to near 6 nT while the Bz component was between +12/-5 nT. Phi angle was mostly negative.
Forecast: Solar wind parameters are expected to continue to be enhanced through 18 Dec under negative polarity CH HSS influence. HSS influences are expected to slowly diminish on 19 Dec.
Forecast: The geomagnetic field is expected to be quiet to active on 17-18 Dec as HSS activity persists. Quiet to unsettled levels is expected on 19 Dec as HSS activity gradually wanes.