NOAA SEC Report of Solar-Geophysical Activity 24 Sep 2001
:Product: Report of Solar-Geophysical Activity :Issued: 2001 Sep 24 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 267 Issued at 2200Z on 24 Sep 2001 IA. Analysis of Solar Active Regions and Activity from 23/2100Z to 24/2100Z: Solar activity was high. Region 9632 (S19E19) produced an X2/2b flare at 1038 UTC. Significant discrete frequency radio bursts (i.e., 7500 sfu at 2695 MHz) accompanied the event, as well as a Type IV sweep which lasted for many hours. A full halo coronal mass ejection was seen by SOHO/LASCO. This region remains bright in H-alpha and still shows mixed polarities in its largest spot. Elsewhere on the disk occasional small flares occurred from a number of the 15 spotted regions visible. Two new regions were assigned, Region 9636 (N12E65) and Region 9637 (S14E71). IB. Solar Activity Forecast: Solar activity is expected to be moderate to high. Region 9632 is still a threat to produce additional M and X class activity. IIA. Geophysical Activity Summary 23/2100Z to 24/2100Z: The geomagnetic field was quiet to unsettled. Satellite proton events at greater than 10 and greater than 100 MeV began shortly after the X2/2b flare. The greater than 10 MeV protons crossed threshold at 1215 UTC, and reached a tentative maximum of 1,020 pfu at 2040 UTC. The greater than 100 MeV event began at 1440 UTC and attained its tentative maximum of 10.6 pfu at 2020 UTC. Neither trace is declining at this writing. In addition a Polar Cap Absorption event began at 1315 UTC, and registered a peak value of 9.0 dB of absorption at 30 MHz at approximately 1935 UTC. IIB. Geophysical Activity Forecast: The geomagnetic field is expected to be at major to severe storm levels beginning early on 26 September. The cme/flare event of earlier today is expected to spawn a strong disturbance expected to persist for 48 hours. The proton events currently occurring are likely to continue for the next 24 hours. The Polar Cap Absorption is expected to continue throughout the day on 25 September. III. Event Probabilities 25 Sep-27 Sep Class M 80/80/80 Class X 30/30/30 Proton 99/50/30 PCAF in progress IV. Penticton 10.7 cm Flux Observed 24 Sep 279 Predicted 25 Sep-27 Sep 285/290/285 90 Day Mean 24 Sep 168 V. Geomagnetic A Indices Observed Afr/Ap 23 Sep 018/027 Estimated Afr/Ap 24 Sep 010/012 Predicted Afr/Ap 25 Sep-27 Sep 015/020-080/100-040/040 VI. Geomagnetic Activity Probabilities 25 Sep-27 Sep A. Middle Latitudes Active 30/05/10 Minor storm 15/25/50 Major-severe storm 05/65/25 B. High Latitudes Active 40/05/10 Minor storm 20/25/40 Major-severe storm 10/70/40
