:Product: 20010411RSGA.txt :Issued: 2001 Apr 11 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 101 Issued at 2200Z on 11 Apr 2001 IA. Analysis of Solar Active Regions and Activity from 10/2100Z to 11/2100Z: Solar activity was moderate. A single M-class event occurred during the period. Region 9415 (S22W27) produced an M2/1f parallel ribbon flare at 11/1326 UTC. This event was accompanied by Type II and IV radio sweeps, a 540 sfu 10 cm radio burst, and a full-halo coronal mass ejection (CME). Two new regions were numbered: 9426 (S09E40) and 9427 (S07W12). IB. Solar Activity Forecast: Solar activity is expected to be at moderate to high levels. Region 9415 can be expected to produce another major flare during the period. IIA. Geophysical Activity Summary 10/2100Z to 11/2100Z: The geomagnetic field ranged from quiet to severe storm levels. Two discernable shocks were detected by the ACE spacecraft at approximately 11/1300 and 11/1520 UTC. These effects were most likely the precursors for the two earth-directed CME's produced on 9-10 April. The resulting CME's arrival at earth produced severe geomagnetic storming during the period of 11/1500-1800 UTC. The greater than 10 MeV proton flux was at high levels all period long, reaching a maximum of 322 PFU near the end of the period. A polar cap absorption (PCA) event remained in effect during the period. The greater than 2 MeV electron flux has at high levels for the first part of the period and then decreased to moderate levels for the remainder of the period. IIB. Geophysical Activity Forecast: The geomagnetic field is expected to continue at active to major storm levels during the first day of the period. A second geomagnetic storm is expected to arrive late on 12 April or early on 13 April UTC. This disturbance will be the result of the full-halo CME described in Section 1A. Brief severe storm levels at high latitudes can be expected. Unsettled to minor storm levels are expected on 14 April as the storm subsides. The greater than 10 MeV proton event is expected to continue through most of the period. The PCA event is expected to end during the latter half of the period. The greater than 2 MeV electron flux is expected to be at mostly moderate levels during the period. III. Event Probabilities 12 Apr-14 Apr Class M 80/80/80 Class X 25/25/25 Proton 80/25/25 PCAF in progress IV. Penticton 10.7 cm Flux Observed 11 Apr 160 Predicted 12 Apr-14 Apr 160/160/155 90 Day Mean 11 Apr 167 V. Geomagnetic A Indices Observed Afr/Ap 10 Apr 007/009 Estimated Afr/Ap 11 Apr 050/060 Predicted Afr/Ap 12 Apr-14 Apr 060/090-050/050-020/025 VI. Geomagnetic Activity Probabilities 12 Apr-14 Apr A. Middle Latitudes Active 15/15/35 Minor storm 25/25/15 Major-severe storm 45/45/10 B. High Latitudes Active 15/25/35 Minor storm 30/30/25 Major-severe storm 50/35/15