:Product: 20010417RSGA.txt :Issued: 2001 Apr 17 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 107 Issued at 2200Z on 17 Apr 2001 IA. Analysis of Solar Active Regions and Activity from 16/2100Z to 17/2100Z: Solar activity has been low. There were several optically uncorrelated C-class events during the period. New Region 9431 (S10E49) was numbered today. IB. Solar Activity Forecast: Solar activity is expected to be low with an isolated chance for a M-class event. IIA. Geophysical Activity Summary 16/2100Z to 17/2100Z: The geomagnetic field was quiet to unsettled. The greater than 10 MeV proton event that started on April 15 is still in progress. The greater than 100 proton event that began at 15/1405 UTC reached a maximum of 146 pfu at 15/1525 UTC and ended at 17/0515 UTC. The polar cap absorption (PCA) event ended at 17/0315 UTC. The greater than 2 MeV electrons at geosynchronous orbit remained at high levels and above threshold through the period. IIB. Geophysical Activity Forecast: The geomagnetic field is expected to be unsettled to active for April 18 and 19 as a result of possible effects from the X14/2b event on April 15, and possible effects from a well positioned coronal hole. Quiet to unsettled conditions are expected to return on April 20. The greater than 10 MeV proton event is expected to go below threshold on April 18. III. Event Probabilities 18 Apr-20 Apr Class M 60/50/50 Class X 01/01/01 Proton 01/01/01 PCAF green IV. Penticton 10.7 cm Flux Observed 17 Apr 126 Predicted 18 Apr-20 Apr 135/145/155 90 Day Mean 17 Apr 165 V. Geomagnetic A Indices Observed Afr/Ap 16 Apr 007/007 Estimated Afr/Ap 17 Apr 008/015 Predicted Afr/Ap 18 Apr-20 Apr 020/025-015/020-010/015 VI. Geomagnetic Activity Probabilities 18 Apr-20 Apr A. Middle Latitudes Active 50/25/20 Minor storm 10/05/05 Major-severe storm 05/01/01 B. High Latitudes Active 50/40/30 Minor storm 15/10/10 Major-severe storm 10/05/05