Joint USAF/NOAA Report of Solar and Geophysical Activity 18 Sep 2008

Product: Report of Solar-Geophysical Activity
Issued: 2008 Sep 18 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 262 Issued at 2200Z on 18 Sep 2008

IA. Analysis of Solar Active Regions and Activity from 17/2100Z to 18/2100Z: Solar activity was very low. No flares were observed during the past 24 hours. The visible disk remained spotless.

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

IIA. Geophysical Activity Summary 17/2100Z to 18/2100Z: The geomagnetic field was predominately quiet to unsettled. An isolated active period was observed at Boulder between 18/0900-1200Z. Solar wind speed measured at the ACE spacecraft showed a gradual decrease from approximately 410 km/s to 370 km/s during the forecast period. The greater than 2 MeV electron flux at geosynchronous orbit was at high levels today.

IIB. Geophysical Activity Forecast: The geomagnetic field is expected to be predominately quiet with isolated unsettled conditions for the next three days (19-21 September).

III. Event Probabilities 19 Sep-21 Sep

• Class M 01/01/01
• Class X 01/01/01
• Proton 01/01/01
• PCAF Green

IV. Penticton 10.7 cm Flux

• Observed 18 Sep 067
• Predicted 19 Sep-21 Sep 066/066/066
• 90 Day Mean 18 Sep 066

V. Geomagnetic A Indices

• Observed Afr/Ap 17 Sep 003/003
• Estimated Afr/Ap 18 Sep 005/005
• Predicted Afr/Ap 19 Sep-21 Sep 005/005-005/005-005/005

VI. Geomagnetic Activity Probabilities 19 Sep-21 Sep

A. Middle Latitudes

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

B. High Latitudes

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