Product: Report of Solar-Geophysical Activity
Issued: 2011 Dec 25 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 359 Issued at 2200Z on 25 Dec 2011
IA. Analysis of Solar Active Regions and Activity from 24/2100Z
to 25/2100Z: Solar activity was moderate. New Region 1387 (S22W28)
produced a M4/1N flare at 25/1816Z. This event was accompanied by
Type II (1019 km/s) and Type IV radio emissions. This region grew
rapidly, ending the period as a Dao type group with Beta magnetic
characteristics. Coronagraph imagery was not yet available to
determine the characteristics of the CME. Earlier in the period, a
filament eruption occurred near N21W15. Analysis of this event
using LASCO imagery indicated a speed near 400 km/s. Evaluation of
the geoeffective potential of both the flare and filament eruption
is ongoing.
IB. Solar Activity Forecast: Solar activity is expected to be
moderate, with a chance for further M-class activity from Region
1387.
IIA. Geophysical Activity Summary 24/2100Z to 25/2100Z:
The geomagnetic field was quiet. An enhancement of the 10 MeV proton
flux at the ACE spacecraft was observed following the M4/1N flare
mentioned earlier.
IIB. Geophysical Activity Forecast: The geomagnetic field is
expected to be mosly quiet on Days 1 and 2 (26-27 December).
Initial predictions are for the CME to arrive late on Day 3 (28
December), bringing unsettled to active levels with a slight chance
for minor storm conditions at high latitudes. The arrival estimate
will be refined as new data becomes available.
III. Event Probabilities 26 Dec-28 Dec
Class M 50/50/50
Class X 05/05/05
Proton 05/05/05
PCAF Green
IV. Penticton 10.7 cm Flux
Observed 25 Dec 144
Predicted 26 Dec-28 Dec 150/155/155
90 Day Mean 25 Dec 144
V. Geomagnetic A Indices
Observed Afr/Ap 24 Dec 002/001
Estimated Afr/Ap 25 Dec 000/001
Predicted Afr/Ap 26 Dec-28 Dec 006/005-006/005-007/007
VI. Geomagnetic Activity Probabilities 26 Dec-28 Dec
A. Middle Latitudes
Active 05/20/25
Minor storm 01/05/15
Major-severe storm 01/05/05
B. High Latitudes
Active 15/15/15
Minor storm 10/20/30
Major-severe storm 05/25/40