Joint USAF/NOAA Report of Solar and Geophysical Activity 17 Aug 2003

SDF Number 229 Issued at 2200Z on 17 Aug 2003

IA. Analysis of Solar Active Regions and Activity from 16/2100Z
to 17/2100Z: Activity was at low levels. Region 431 (S10W38)
produced a C2 flare at 17/0426Z. Region 431 continues its slow
decay and has simplified to a beta-gamma magnetic configuration.
New Region 436 (N07E69) was numbered today

IB. Solar Activity Forecast: Solar activity is expected to be at
low levels with the chance of an isolated M-class event from Region
431.

IIA. Geophysical Activity Summary 16/2100Z to 17/2100Z:
The geomagnetic field was quiet early in the day and active late in
the day. At 1340Z, a shock passed the NASA/ACE spacecraft with a
100 km/s increase in solar wind speed to 540 km/s and an increase in
B-total to over 20 nT. The Bz component of the IMF remained
northward during this time, resulting in active conditions on Earth.

IIB. Geophysical Activity Forecast: The geomagnetic field is
expected to be at quiet to active levels on day one due to residual
effects from the shock. Quiet to unsettled levels are expected on
day two and day three.

III. Event Probabilities 18 Aug-20 Aug

• Class M 30/25/25
• Class X 05/05/05
• Proton 01/01/01
• PCAF green

IV. Penticton 10.7 cm Flux

• Observed 17 Aug 119
• Predicted 18 Aug-20 Aug 125/130/125
• 90 Day Mean 17 Aug 127

V. Geomagnetic A Indices

• Observed Afr/Ap 16 Aug 007/011
• Estimated Afr/Ap 17 Aug 012/015
• Predicted Afr/Ap 18 Aug-20 Aug 010/012-008/010-008/010

VI. Geomagnetic Activity Probabilities 18 Aug-20 Aug

A. Middle Latitudes

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

B. High Latitudes

• Active 25/25/25
• Minor storm 10/10/10
• Major-severe storm 01/01/01