:Product: 20010408RSGA.txt :Issued: 2001 Apr 08 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 098 Issued at 2200Z on 08 Apr 2001 IA. Analysis of Solar Active Regions and Activity from 07/2100Z to 08/2100Z: Solar activity decreased to very low levels. Region 9415 (S21E05) produced no flares during the period, but remained large and complex with a persistent magnetic delta structure within its lead sunspot. The remaining regions were simply structured and stable, including newly numbered Regions 9423 (N21E03) and 9424 (S16E34). IB. Solar Activity Forecast: Solar activity is expected to be at moderate to high levels. Region 9415 may produce a major flare during the period. IIA. Geophysical Activity Summary 07/2100Z to 08/2100Z: Geomagnetic field activity ranged from quiet to major storm levels. Quiet to unsettled levels occurred through 08/1030 UTC. A CME-related shock front reached the ACE spacecraft at 08/1034 UTC followed by a sudden impulse (SI) at 08/1101 UTC (58 nT, as measured by the Boulder magnetometer). Field activity increased to active to major storm levels following the SI. The CME source was the X5 flare of 06 April. The greater than 10 MeV proton flux at geosynchronous orbit remained enhanced, but slowly decreased through the period. IIB. Geophysical Activity Forecast: Active to major geomagnetic storm conditions are expected during the first day as CME effects continue. Unsettled conditions are expected during the remainder of the period. There will be a chance for a proton flare from Region 9415 during the period. III. Event Probabilities 09 Apr-11 Apr Class M 80/80/80 Class X 25/25/25 Proton 25/25/25 PCAF yellow IV. Penticton 10.7 cm Flux Observed 08 Apr 169 Predicted 09 Apr-11 Apr 165/165/160 90 Day Mean 08 Apr 167 V. Geomagnetic A Indices Observed Afr/Ap 07 Apr 017/016 Estimated Afr/Ap 08 Apr 030/040 Predicted Afr/Ap 09 Apr-11 Apr 025/030-015/015-012/012 VI. Geomagnetic Activity Probabilities 09 Apr-11 Apr A. Middle Latitudes Active 40/30/25 Minor storm 20/15/10 Major-severe storm 10/05/05 B. High Latitudes Active 40/35/30 Minor storm 35/20/15 Major-severe storm 15/10/05