NOAA SEC Report of Solar-Geophysical Activity 12 Apr 2001
:Product: Report of Solar-Geophysical Activity :Issued: 2001 Apr 12 2200 UT # 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 102 Issued at 2200Z on 12 Apr 2001 IA. Analysis of Solar Active Regions and Activity from 11/2100Z to 12/2100Z: Solar activity was high. Region 9415 (S22W43) produced an X2 flare at 12/1028 UTC. This flare was not optically correlated at the peak time of the event, however EIT imagery and later optical flare observations have associated this flare with Region 9415. This event was accompanied by Type II and IV radio sweeps, a 1200 sfu 10 cm radio burst, and a full-halo coronal mass ejection (CME). Region 9415 also produced an M1/1n event at 12/0304 UTC. Several other regions developed into more complex sunspot classification groups, but showed very little activity during the period. IB. Solar Activity Forecast: Solar activity is expected to be at moderate to high levels. Region 9415 could possibly produce another major flare during the period. IIA. Geophysical Activity Summary 11/2100Z to 12/2100Z: The geomagnetic field ranged from unsettled to severe storm levels. The geomagnetic field continued to be disturbed early in the period due to CME shock arrivals at earth on 11 April. The storm subsided to unsettled conditions toward the end of the period. The solar radiation storm that was in progress for the last two days has been extended by protons produced from today's X2 event. The greater than 10 MeV proton flux was at high levels all period. The greater than 100 MeV protons reached threshold levels at 12/1305 UTC and remained at or above threshold levels for the remainder of the period. A polar cap absorption (PCA) event was in effect for most of the period. IIB. Geophysical Activity Forecast: The geomagnetic field is expected to be quiet to active for the first part of the period until the arrival of an earth directed CME from the M2/1f event that occurred on 11/1326 UTC. This CME should arrive at earth sometime late on 13 April or early 14 April UTC. A second CME from today's X2 event should arrive at earth late on 14 April or early 15 April UTC. Both arrivals should produce active to major storm levels with brief severe storm levels at high latitudes possible. 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. III. Event Probabilities 13 Apr-15 Apr Class M 80/80/80 Class X 25/25/25 Proton 80/60/25 PCAF in progress IV. Penticton 10.7 cm Flux Observed 12 Apr 149 Predicted 13 Apr-15 Apr 150/145/140 90 Day Mean 12 Apr 167 V. Geomagnetic A Indices Observed Afr/Ap 11 Apr 069/060 Estimated Afr/Ap 12 Apr 045/050 Predicted Afr/Ap 13 Apr-15 Apr 040/020-050/050-025/040 VI. Geomagnetic Activity Probabilities 13 Apr-15 Apr A. Middle Latitudes Active 15/15/35 Minor storm 20/25/15 Major-severe storm 40/45/10 B. High Latitudes Active 35/25/40 Minor storm 25/30/25 Major-severe storm 15/40/20
