Joint USAF/NOAA Report of Solar and Geophysical Activity 28 Sep 2007

Product: Report of Solar-Geophysical Activity
Issued: 2007 Sep 28 2200 UTC
Prepared jointly by the U.S. Dept. of Commerce, NOAA,
Space Environment Center and the U.S. Air Force.

Joint USAF/NOAA Report of Solar and Geophysical Activity
SDF Number 271 Issued at 2200Z on 28 Sep 2007

IA. Analysis of Solar Active Regions and Activity from 27/2100Z to 28/2100Z: Solar activity was very low. No flares occurred during the past 24 hours. Newly numbered Region 971 (N03E07) emerged on disk and is a small, C-type sunspot group.

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

IIA. Geophysical Activity Summary 27/2100Z to 28/2100Z: The geomagnetic field was unsettled to active from 27/2100Z through 28/1200Z. Conditions were quiet from 1200-1800Z but returned to unsettled to active from 1800-2100Z. Real-time solar wind measurements from ACE showed a steady increase in solar wind speed from about 27/1700Z through about 28/0900Z. After 0900Z solar wind speed began to decline, but a second increase in speed and total field began around 1500Z and has continued through forecast issue time 28/2100Z. Both increases show signatures consistent with a coronal hole high speed stream.

IIB. Geophysical Activity Forecast: The geomagnetic field is expected to be mostly active with a chance for minor storm periods at high latitudes for the first day (29 September) due to the continuation of the high speed stream. Activity is expected to decrease to mostly unsettled levels for the second day (30 September) and should be quiet to unsettled on the third day (01 October).

III. Event Probabilities 29 Sep-01 Oct

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

IV. Penticton 10.7 cm Flux

• Observed 28 Sep 067
• Predicted 29 Sep-01 Oct 067/067/067
• 90 Day Mean 28 Sep 069

V. Geomagnetic A Indices

• Observed Afr/Ap 27 Sep 010/019
• Estimated Afr/Ap 28 Sep 015/018
• Predicted Afr/Ap 29 Sep-01 Oct 020/025-010/012-007/008

VI. Geomagnetic Activity Probabilities 29 Sep-01 Oct

A. Middle Latitudes

• Active 40/25/10
• Minor storm 20/15/05
• Major-severe storm 10/05/01

B. High Latitudes

• Active 45/25/15
• Minor storm 25/15/10
• Major-severe storm 15/10/01