:Product: 20010420RSGA.txt :Issued: 2001 Apr 20 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 110 Issued at 2200Z on 20 Apr 2001 IA. Analysis of Solar Active Regions and Activity from 19/2100Z to 20/2100Z: Solar activity was moderate. The largest flare was an M4/1F at 20/2004 UTC in Region 9433 (N17E52). This area also produced an M1/1F at 20/0523 UTC. The region remains a moderately-sized F-type sunspot group with some mixed polarities in the central portions and a total area similar to yesterday's. Region 9432 (N08W06) also produced C-class subflares. Today's Penticton F10.7 noon reading was taken during the M4, resulting in a flare-enhanced value of 180 sfu. IB. Solar Activity Forecast: Solar activity is expected to be moderate. Additional M-class activity in Region 9433 is likely with the possibility of an isolated major flare. IIA. Geophysical Activity Summary 19/2100Z to 20/2100Z: The geomagnetic field was quiet to unsettled. The greater than 10 MeV proton event dropped below the 10 pfu event threshold at 20/1015 UTC (start 18/0315 UTC and 321 pfu peak at 18/1045 UTC) and continues to slowly decay. IIB. Geophysical Activity Forecast: The geomagnetic field is expected to be quiet to unsettled. A major flare in Region 9433 could generate another greater than 10 MeV proton event. III. Event Probabilities 21 Apr-23 Apr Class M 75/75/75 Class X 10/10/10 Proton 05/05/05 PCAF green IV. Penticton 10.7 cm Flux Observed 20 Apr 180 Predicted 21 Apr-23 Apr 175/185/195 90 Day Mean 20 Apr 165 V. Geomagnetic A Indices Observed Afr/Ap 19 Apr 005/007 Estimated Afr/Ap 20 Apr 008/010 Predicted Afr/Ap 21 Apr-23 Apr 005/010-005/010-010/010 VI. Geomagnetic Activity Probabilities 21 Apr-23 Apr A. Middle Latitudes Active 10/10/10 Minor storm 05/05/05 Major-severe storm 01/01/01 B. High Latitudes Active 15/15/15 Minor storm 10/10/10 Major-severe storm 01/01/01