:Product: 20010413RSGA.txt :Issued: 2001 Apr 13 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 103 Issued at 2200Z on 13 Apr 2001 IA. Analysis of Solar Active Regions and Activity from 12/2100Z to 13/2100Z: Solar activity was very low. Region 9415 (S22W59) declined in size and number of spots during the period. This region still retains a beta-gamma-delta magnetic configuration and is still capable of producing M and X-class events. Region 9418 (N26W46) developed into a more magnetically complex beta-gamma configuration, however it produced very little activity today. IB. Solar Activity Forecast: Solar activity is expected to be low to moderate. Region 9415 is still capable of producing another major flare before it rotates over the western limb. IIA. Geophysical Activity Summary 12/2100Z to 13/2100Z: The geomagnetic field was at quiet to severe storm levels. A coronal mass ejection (CME), from an M2 flare on 11 April, impacted earth at 13/0735 UTC. A sudden impact of 19 nT was detected at the Boulder USGS magnetometer. The resulting disturbance caused major and severe geomagnetic storm conditions from 13/1900-2100 UTC, and minor to major storm conditions from 13/1200-1500 UTC. Conditions subsided to active levels for the remainder of the period. The greater than 10 MeV proton event ended at 13/1800 UTC. The polar cap absorption event (PCA) ended during the period. IIB. Geophysical Activity Forecast: The geomagnetic field is expected to be unsettled to minor storming for the first two days of the period. These conditions will be the result of another impact at earth of a CME. This CME originated from an X2 event on 12 April. The expected arrival time is mid to late 14 April and at onset could cause major storm levels, with brief severe storm levels at high latitudes possible. Conditions should subside to quiet to active levels on the third day. III. Event Probabilities 14 Apr-16 Apr Class M 80/70/60 Class X 25/15/10 Proton 25/15/10 PCAF green IV. Penticton 10.7 cm Flux Observed 13 Apr 137 Predicted 14 Apr-16 Apr 135/130/140 90 Day Mean 13 Apr 166 V. Geomagnetic A Indices Observed Afr/Ap 12 Apr 029/038 Estimated Afr/Ap 13 Apr 025/035 Predicted Afr/Ap 14 Apr-16 Apr 050/055-025/030-015/015 VI. Geomagnetic Activity Probabilities 14 Apr-16 Apr A. Middle Latitudes Active 25/35/25 Minor storm 40/15/10 Major-severe storm 30/10/06 B. High Latitudes Active 25/35/35 Minor storm 30/25/20 Major-severe storm 40/20/12