:Product: 1217RSGA.txt :Issued: 2007 Dec 17 2203 UTC # Prepared jointly by the U.S. Dept. of Commerce, NOAA, # Space Weather Prediction Center and the U.S. Air Force. # Joint USAF/NOAA Report of Solar and Geophysical Activity SDF Number 351 Issued at 2200Z on 17 Dec 2007 IA. Analysis of Solar Active Regions and Activity from 16/2100Z to 17/2100Z: Solar activity was low. Region 978 (S10W78) produced today's only C-class event, a C2 at 0716Z. The region appears to be decaying as it approaches west limb. IB. Solar Activity Forecast: Solar activity is expected to be very low, although there continues to be a chance for an isolated C-class event. IIA. Geophysical Activity Summary 16/2100Z to 17/2100Z: The geomagnetic field ranged from quiet to minor storm levels. The field was initially quiet but became disturbed after a sudden impulse was observed at 0300Z. The sudden impulse was preceded by a weak shock in the solar wind observed at ACE at 0204Z. The shock was followed by an increase in velocity and magnetic field at ACE consistent with a corotating interaction region which was then followed by a high speed stream. Active to minor storm conditions prevailed from 0600-1200Z, followed by mostly active conditions. As of forecast issue time the solar wind velocity remains elevated with values around 550-600 km/s. IIB. Geophysical Activity Forecast: Geomagnetic activity is expected to be unsettled to active for the next three days (18-20 December), due to continued influence of the high speed stream. III. Event Probabilities 18 Dec-20 Dec Class M 01/01/01 Class X 01/01/01 Proton 01/01/01 PCAF Green IV. Penticton 10.7 cm Flux Observed 17 Dec 080 Predicted 18 Dec-20 Dec 075/070/070 90 Day Mean 17 Dec 071 V. Geomagnetic A Indices Observed Afr/Ap 16 Dec 001/002 Estimated Afr/Ap 17 Dec 022/025 Predicted Afr/Ap 18 Dec-20 Dec 015/015-015/015-015/015 VI. Geomagnetic Activity Probabilities 18 Dec-20 Dec A. Middle Latitudes Active 50/50/50 Minor storm 20/20/20 Major-severe storm 05/05/05 B. High Latitudes Active 50/50/50 Minor storm 25/25/25 Major-severe storm 10/10/10