:Product: 20010823RSGA.txt :Issued: 2001 Aug 23 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 235 Issued at 2200Z on 23 Aug 2001 IA. Analysis of Solar Active Regions and Activity from 22/2100Z to 23/2100Z: Solar activity decreased to low levels. Region 9591 (S17E53) produced frequent, impulsive mid-level C-class flares with minor radio emission. This region showed a magnetic delta structure in its trailing sunspots and a weak delta in its interior spots. Currently, Region 9591 spans about 30 degrees in longitude. However, it appeared likely this region was comprised of two abutted sunspot groups, which may be split into separate groups once this complex rotates further into view. Minor polarity mixing was evident in Regions 9582 (N28W33) and 9585 (N14W16), but both regions were inactive as they showed signs of decay. The remaining active regions were unremarkable. New Region 9593 (N00E01) was numbered. IB. Solar Activity Forecast: Solar activity is expected to be moderate with a good chance for an isolated M-class flare from Region 9591. There is also a slight chance for a major flare from this region. IIA. Geophysical Activity Summary 22/2100Z to 23/2100Z: Geomagnetic field activity decreased to quiet to unsettled levels as coronal hole effects subsided. IIB. Geophysical Activity Forecast: Geomagnetic field activity is expected to be at quiet to unsettled levels during the first half of the period increasing to unsettled to active levels during the rest of the period. There will be a slight chance for a proton event during the period. The greater than 2 MeV electron flux at geosynchronous orbit may reach high levels during the first half of the forecast period. III. Event Probabilities 24 Aug-26 Aug Class M 50/50/50 Class X 10/10/10 Proton 05/10/10 PCAF green IV. Penticton 10.7 cm Flux Observed 23 Aug 170 Predicted 24 Aug-26 Aug 175/180/180 90 Day Mean 23 Aug 152 V. Geomagnetic A Indices Observed Afr/Ap 22 Aug 014/017 Estimated Afr/Ap 23 Aug 009/010 Predicted Afr/Ap 24 Aug-26 Aug 010/010-012/012-015/012 VI. Geomagnetic Activity Probabilities 24 Aug-26 Aug A. Middle Latitudes Active 20/25/30 Minor storm 05/10/15 Major-severe storm 01/01/05 B. High Latitudes Active 25/30/35 Minor storm 10/15/20 Major-severe storm 01/01/10