:Product: 20010427RSGA.txt :Issued: 2001 Apr 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 117 Issued at 2200Z on 27 Apr 2001 IA. Analysis of Solar Active Regions and Activity from 26/2100Z to 27/2100Z: Solar activity was moderate. Region 9433 (N18W39) produced an M1/1f flare at 27/1915 UTC along with isolated C-class subflares. Region 9433 began to gradually decay following yesterday's M7/2b flare with decreased spot count and penumbral coverage. However, a magnetic delta configuration persisted in the trailer portion of the region, where most flare activity has occurred. Region 9441 (N08E38) produced isolated subflares as it gradually increased in spot count and penumbral coverage, though it remained a moderate-sized, simply-structured spot group. New Region 9443 (S10E21), a small simple bipole, was numbered. IB. Solar Activity Forecast: Activity is expected to be at moderate to high levels. Region 9433 is expected to produce mostly low-level M-class flares. However, it may produce an isolated major flare during the period. IIA. Geophysical Activity Summary 26/2100Z to 27/2100Z: Geomagnetic field activity was at quiet to unsettled levels. The greater than 10 MeV electron flux became enhanced following yesterdays M7/2b flare, but did not reach event levels. IIB. Geophysical Activity Forecast: A geomagnetic disturbance is expected to commence during the latter half of 28 April and continue into 29 April following yesterday's M7/2b flare and associated full-halo CME . Active to major storm levels will be possible during this disturbance. Mostly unsettled levels are expected during 30 April. The greater than 10 MeV proton flux could increase to event levels on 28 April. Region 9433 may produce a proton flare during the period. III. Event Probabilities 28 Apr-30 Apr Class M 75/75/75 Class X 20/20/20 Proton 20/20/20 PCAF yellow IV. Penticton 10.7 cm Flux Observed 27 Apr 191 Predicted 28 Apr-30 Apr 185/180/175 90 Day Mean 27 Apr 167 V. Geomagnetic A Indices Observed Afr/Ap 26 Apr 008/007 Estimated Afr/Ap 27 Apr 005/008 Predicted Afr/Ap 28 Apr-30 Apr 015/010-040/040-012/020 VI. Geomagnetic Activity Probabilities 28 Apr-30 Apr A. Middle Latitudes Active 25/30/40 Minor storm 20/35/20 Major-severe storm 05/10/05 B. High Latitudes Active 30/25/45 Minor storm 25/40/25 Major-severe storm 10/15/10