Report of Solar-Geophysical Activity
Issued: 2005 Sep 07 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 250 Issued at 2200Z on 07 Sep 2005 IA. Analysis of Solar Active Regions and Activity from 06/2100Z to 07/2100Z: Solar activity increased to high levels this period as newly numbered Region 808 (S12E83) produced one of the largest solar flares of Cycle 23. An X17/3b white light flare erupted in this region at 07/1740Z. A large and fast CME was visible on the MK4 coronagraph at Mauna Loa. Intense centimetric radio bursts accompanied this flare, including a 27,000 sfu Tenflare. Type II (1860 km/s) and Type IV radio sweeps were also observed. This region also produced a very long duration M1 flare, which peaked at 06/2202Z. A fast and bright CME (1400 km/s) on LASCO imagery was observed with this event. The sunspot cluster associated with Region 808 is just now rotating into view, so an accurate assessment of its true size and complexity will have to wait. Region 808 is the return of old Region 798, which produced significant solar and geophysical activity during its last passage on the visible disk.
IB. Solar Activity Forecast: Solar activity is expected to be moderate to high. Region 808 is obviously a complex and moderate-large size sunspot group with great flare potential. Expect further major flares.
IIA. Geophysical Activity Summary 06/2100Z to 07/2100Z:
The geomagnetic field was quiet to active. Today's powerful X17 flare produced a sudden disturbance in the geomagnetic field at 07/1725Z.
This 82 nT magnetic crochet was one of the largest observed this Solar Cycle. A slow rise in the greater than 10 MeV protons at geosynchronous orbit began near issue time. The greater than 2 MeV electron flux at geosynchronous orbit reached high levels again today.
IIB. Geophysical Activity Forecast: The geomagnetic field is expected to continue at quiet to unsettled levels with isolated active periods. The CME activity associated with yesterday's long-duration M1 and today's X17 flares were not Earth directed. The greater than 10 MeV protons at geosynchronous orbit are slowly rising now and are expected to continue to do so. These protons will likely cross the 10 pfu threshold on 08 Sep.
III. Event Probabilities 08 Sep-10 Sep
Class M 70/75/75
Class X 30/30/30
Proton 60/50/40
PCAF yellow
IV. Penticton 10.7 cm Flux
Observed 07 Sep 100
Predicted 08 Sep-10 Sep 110/120/120
90 Day Mean 07 Sep 091
V. Geomagnetic A Indices
Observed Afr/Ap 06 Sep 006/009
Estimated Afr/Ap 07 Sep 010/010
Predicted Afr/Ap 08 Sep-10 Sep 008/012-010/015-005/010 VI. Geomagnetic Activity Probabilities 08 Sep-10 Sep A. Middle Latitudes
Active 20/20/15
Minor storm 05/05/05
Major-severe storm 01/01/01
B. High Latitudes
Active 25/25/20
Minor storm 10/10/05
Major-severe storm 01/01/01