Joint USAF/NOAA Report of Solar and Geophysical Activity 27 Sep 2007

Product: Report of Solar-Geophysical Activity
Issued: 2007 Sep 27 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 270 Issued at 2200Z on 27 Sep 2007

IA. Analysis of Solar Active Regions and Activity from 26/2100Z to 27/2100Z: Solar activity was very low. No flares occurred during the past 24 hours.

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

IIA. Geophysical Activity Summary 26/2100Z to 27/2100Z: The geomagnetic field was initially quiet. However, a weak shock was seen at ACE at 1054Z, followed by an increase in magnetic field strength and density as well as a small increase in velocity. There were some extended intervals of southward Bz and as a result there was a period of minor to major storm level activity from 1500-1800Z. Conditions declined to active to minor storm levels for remainder of the period (1800-2100Z). Although the observations are not yet conclusive the disturbance appears to be from a transient structure in the solar wind, rather than from a recurrent structure. The greater than 2 MeV electron flux at geosynchronous orbit reached high levels during the past 24 hours.

IIB. Geophysical Activity Forecast: The geomagnetic field is expected to be unsettled with occasional active periods for the first day (28 September) due to the anticipated onset of a high speed stream from a coronal hole. Activity should strengthen on the second day (29 September) to predominantly active levels with a chance for minor storm periods at high latitudes. Conditions should decline to predominantly unsettled levels on the third day (30 September).

III. Event Probabilities 28 Sep-30 Sep

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

• IV. Penticton 10.7 cm Flux
• Observed 27 Sep 067
• Predicted 28 Sep-30 Sep 067/067/067
• 90 Day Mean 27 Sep 069

V. Geomagnetic A Indices

• Observed Afr/Ap 26 Sep 002/003
• Estimated Afr/Ap 27 Sep 010/015
• Predicted Afr/Ap 28 Sep-30 Sep 010/015-020/025-010/012

VI. Geomagnetic Activity Probabilities 28 Sep-30 Sep

A. Middle Latitudes

• Active 40/40/30
• Minor storm 15/25/15
• Major-severe storm 05/10/05

B. High Latitudes

• Active 45/45/35
• Minor storm 20/25/20
• Major-severe storm 10/15/10