Joint USAF/NOAA Report of Solar and Geophysical Activity 20 Aug 2004

Prepared jointly by the U.S. Dept. of Commerce, NOAA,
Space Environment Center and the U.S. Air Force.

Updated 2004 Aug 20 2200 UTC

Joint USAF/NOAA Report of Solar and Geophysical Activity
SDF Number 233 Issued at 2200Z on 20 Aug 2004

IA. Analysis of Solar Active Regions and Activity from 19/2100Z
to 20/2100Z: Solar activity has been low. Region 656 (S13,L=87),
which is behind the west limb, produced a C2.1 at 19/2105 UTC and a
C2.8 flare at 20/0107 UTC. Both events were long duration flares.
Regions 661 (N08W19), 662 (N13E00) and 663 (N10E67) all exhibited
slight growth in size over the period, with stable magnetic
complexity. New spots have appeared on the east limb next to Region
663. Further observations will determine if these spots are part of
Region 663. New Region 664 (S11E40) was numbered today.

IB. Solar Activity Forecast: Solar activity is expected to be low.
Region 661 may produce C- and isolated M-class flares.

IIA. Geophysical Activity Summary 19/2100Z to 20/2100Z:
The geomagnetic field has been quiet to active from the effects of a
small geoeffective coronal hole.

IIB. Geophysical Activity Forecast: The geomagnetic field is
expected to be quiet to unsettled, with possible active conditions
on 22 August from the effects of a coronal hole moving into
geoeffective position.

III. Event Probabilities 21 Aug-23 Aug

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

IV. Penticton 10.7 cm Flux

• Observed 20 Aug 121
• Predicted 21 Aug-23 Aug 120/115/110
• 90 Day Mean 20 Aug 109

V. Geomagnetic A Indices

• Observed Afr/Ap 19 Aug 003/007
• Estimated Afr/Ap 20 Aug 012/015
• Predicted Afr/Ap 21 Aug-23 Aug 008/008-008/015-012/015

VI. Geomagnetic Activity Probabilities 21 Aug-23 Aug

A. Middle Latitudes

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

B. High Latitudes

• Active 30/40/40
• Minor storm 05/05/10
• Major-severe storm 01/01/01