Joint USAF/NOAA Report of Solar and Geophysical Activity 25 Dec 2002

SDF Number 359 Issued at 2200Z on 25 Dec 2002

IA. Analysis of Solar Active Regions and Activity from 24/2100Z
to 25/2100Z: Solar activity was at low levels. The largest event
was an optically uncorrelated C4.8 flare at 25/0546 UTC. Two of the
most active regions over the past week, Region 224 (S14W92) and
Region 226 (S28, L=122), rotated beyond the west limb today. Region
230 (S08W50) continues to decay and has lost its trailing spots.
The region is now a simple Hax spot group with an alpha magnetic
configuration. New Region 235 (N13E28) was numbered today.

IB. Solar Activity Forecast: Solar activity is expected to be low.

IIA. Geophysical Activity Summary 24/2100Z to 25/2100Z:
The geomagnetic field was predominantly at unsettled levels. One
period of isolated active conditions occurred. Solar wind velocity
gradually decreased throughout the day from 540 km/s to 440 km/s and
Bz was slightly negative for most of the day. The greater than 2
MeV electron flux at geo-synchronous orbit reached high levels
today.

IIB. Geophysical Activity Forecast: The geomagnetic field is
expected to be quiet to active. A large positive polarity coronal
hole will rotate into a geo-effective position on day two of the
period. Unsettled to active conditions are expected for day two and
day three.

III. Event Probabilities 26 Dec-28 Dec

• Class M 20/20/15
• Class X 01/01/01
• Proton 01/01/01
• PCAF green

IV. Penticton 10.7 cm Flux

• Observed 25 Dec 132
• Predicted 26 Dec-28 Dec 130/125/120
• 90 Day Mean 25 Dec 167

V. Geomagnetic A Indices

• Observed Afr/Ap 24 Dec 014/018
• Estimated Afr/Ap 25 Dec 012/015
• Predicted Afr/Ap 26 Dec-28 Dec 010/015-015/018-020/025

VI. Geomagnetic Activity Probabilities 26 Dec-28 Dec
A. Middle Latitudes

• Active 10/20/30
• Minor storm 01/10/15
• Major-severe storm 01/01/01

B. High Latitudes

• Active 15/25/35
• Minor storm 05/10/20
• Major-severe storm 01/05/10