:Product: 1218RSGA.txt :Issued: 2023 Dec 18 2200 UTC # Prepared jointly by the U.S. Dept. of Commerce, NOAA, # Space Weather Prediction Center and the U.S. Air Force. # Joint USAF/NOAA Solar Geophysical Activity Report and Forecast SDF Number 352 Issued at 2200Z on 18 Dec 2023 IA. Analysis of Solar Active Regions and Activity from 17/2100Z to 18/2100Z: Solar activity has been at low levels for the past 24 hours. The largest solar event of the period was a C6 event observed at 18/1422Z from Region 3528 (N09E12). There are currently 9 numbered sunspot regions on the disk. IB. Solar Activity Forecast: Solar activity is expected to be low with a chance for M-class flares on day one (19 Dec) and expected to be low with a slight chance for an M-class flare on days two and three (20 Dec, 21 Dec). IIA. Geophysical Activity Summary 17/2100Z to 18/2100Z: The geomagnetic field has been at unsettled to major storm levels for the past 24 hours. Solar wind speed reached a peak of 581 km/s at 18/2036Z. Total IMF reached 13 nT at 18/1036Z. The maximum southward component of Bz reached -11 nT at 18/1034Z. Electrons greater than 2 MeV at geosynchronous orbit reached a peak level of 102 pfu. IIB. Geophysical Activity Forecast: The geomagnetic field is expected to be at quiet to active levels on days one and two (19 Dec, 20 Dec) and quiet to unsettled levels on day three (21 Dec). III. Event probabilities 19 Dec-21 Dec Class M 25/20/20 Class X 05/01/01 Proton 01/01/01 PCAF green IV. Penticton 10.7 cm Flux Observed 18 Dec 161 Predicted 19 Dec-21 Dec 162/162/164 90 Day Mean 18 Dec 149 V. Geomagnetic A Indices Observed Afr/Ap 17 Dec 032/044 Estimated Afr/Ap 18 Dec 017/027 Predicted Afr/Ap 19 Dec-21 Dec 014/015-010/012-007/010 VI. Geomagnetic Activity Probabilities 19 Dec-21 Dec A. Middle Latitudes Active 30/25/15 Minor Storm 10/10/05 Major-severe storm 01/01/01 B. High Latitudes Active 15/15/15 Minor Storm 20/20/15 Major-severe storm 20/20/10