Joint USAF/NOAA Report of Solar and Geophysical Activity 17 Dec 2007

Product: Report of Solar-Geophysical Activity
Issued: 2007 Dec 17 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 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