:Product: 1218RSGA.txt :Issued: 2015 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 2015 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 C4 event observed at 18/0509Z from Region 2469 (N19W15). There are currently 3 numbered sunspot regions on the disk. IB. Solar Activity Forecast: Solar activity is likely to be low with a slight chance for an M-class flare on days one, two, and three (19 Dec, 20 Dec, 21 Dec). IIA. Geophysical Activity Summary 17/2100Z to 18/2100Z: The geomagnetic field has been at quiet levels for the past 24 hours. Solar wind speed, as measured by the ACE spacecraft, reached a peak speed of 508 km/s at 17/2112Z. Total IMF reached 6 nT at 17/2232Z. The maximum southward component of Bz reached -5 nT at 17/2113Z. Electrons greater than 2 MeV at geosynchronous orbit reached a peak level of 933 pfu. IIB. Geophysical Activity Forecast: The geomagnetic field is expected to be at active to major storm levels on day one (19 Dec), quiet to active levels on day two (20 Dec) and quiet to unsettled levels on day three (21 Dec). III. Event probabilities 19 Dec-21 Dec Class M 15/15/15 Class X 01/01/01 Proton 01/01/01 PCAF green IV. Penticton 10.7 cm Flux Observed 18 Dec 117 Predicted 19 Dec-21 Dec 115/115/115 90 Day Mean 18 Dec 109 V. Geomagnetic A Indices Observed Afr/Ap 17 Dec 006/006 Estimated Afr/Ap 18 Dec 008/009 Predicted Afr/Ap 19 Dec-21 Dec 030/042-014/018-007/008 VI. Geomagnetic Activity Probabilities 19 Dec-21 Dec A. Middle Latitudes Active 35/30/15 Minor Storm 35/10/05 Major-severe storm 15/01/01 B. High Latitudes Active 05/15/20 Minor Storm 20/35/25 Major-severe storm 70/40/20