Joint USAF/NOAA Report of Solar and Geophysical Activity 20 Dec 2002

SDF Number 354 Issued at 2200Z on 20 Dec 2002

IA. Analysis of Solar Active Regions and Activity from 19/2100Z
to 20/2100Z: Solar activity increased to high levels. Along with
several lesser C-class flares Region 226 (N19W16) produced an
M6.8/Sf major flare (optical classification has some doubt due to
the seeing conditions) at 20/1318 UTC. A Type II radio sweep
(estimated shock velocity of 868 km/sec), Tenflare, and strong
discrete radio busts accompanied the flare. This region has
undergone little change from yesterday and retains it’s
beta-gamma-delta magnetic classification. Region 229 (N19W16)
produced a near long duration M2.7/2n flare at 19/2153 UTC that had
a Type II radio sweep with an estimated shock velocity of 668
km/sec. A Type IV radio sweep, Tenflare, and multiple discrete
radio bursts were associated with the flare. SOHO/LASCO C2 and C3
imagery indicate a possible earth-bound CME as a result of this
activity. Region 230 (S08E19) continues to show steady growth and
was responsible for several minor C-class flares today. No new
regions were numbered today.

IB. Solar Activity Forecast: Solar activity is expected to be at
moderate levels. Regions 226, 229, and 230 all have the potential
for M-class production. Region 226 remains capable of producing an
isolated major flare.

IIA. Geophysical Activity Summary 19/2100Z to 20/2100Z:
The geomagnetic field was at quiet to minor storm levels. The
elevated conditions are due to a geoeffective recurrent positive
polarity coronal hole high speed stream. The greater than 10 MeV
proton flux at geosynchronous orbit became elevated following the
M2.7 event early in the period while the greater than 2 MeV electron
flux reached moderate levels late in the day.

IIB. Geophysical Activity Forecast: The geomagnetic field is
expected to be at predominantly quiet to unsettled levels for day
one of the forecast period. A shock passage is expected on day two
due to the M2.7 event (discussed in part IA) which may result in
active to minor storm conditions. By day three a return to
predominantly quiet unsettled levels is expected.

III. Event Probabilities 21 Dec-23 Dec

• Class M 70/70/70
• Class X 15/15/15
• Proton 10/10/10
• PCAF green

IV. Penticton 10.7 cm Flux

• Observed 20 Dec 197
• Predicted 21 Dec-23 Dec 195/195/185
• 90 Day Mean 20 Dec 166

V. Geomagnetic A Indices

• Observed Afr/Ap 19 Dec 015/021
• Estimated Afr/Ap 20 Dec 012/015
• Predicted Afr/Ap 21 Dec-23 Dec 010/015-025/025-012/015

VI. Geomagnetic Activity Probabilities 21 Dec-23 Dec
A. Middle Latitudes

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

B. High Latitudes

• Active 25/45/25
• Minor storm 10/30/10
• Major-severe storm 05/10/05