:Product: 20010930RSGA.txt :Issued: 2001 Sep 30 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 273 Issued at 2200Z on 30 Sep 2001 IA. Analysis of Solar Active Regions and Activity from 29/2100Z to 30/2100Z: Solar activity remained at moderate levels. Region 9628 (S17W76) produced a long-duration M1/Sf flare at 30/1141 UTC associated with minor discrete frequency radio emission. Region 9628 may have decayed a bit as it approached the west limb, but remained large and complex. Decay was also noted in Region 9632 (S18W61) as its large interior spot mass began to split, which may have dissipated the magnetic delta structure contained therein. Nonetheless, this region remained large and complex. Region 9636 (N14W15), a reverse-polarity sunspot group, showed gradual development during the day. It was moderate in size and complexity as it produced isolated subflares, none of which were associated with significant X-ray or radio emission. IB. Solar Activity Forecast: Solar activity is expected to remain at moderate levels. Isolated M-class flares will be possible from Regions 9628, 9632, and 9636. Regions 9628 and 9632 each could produce an isolated major flare before they rotate out of view on 01 and 02 October, respectively. IIA. Geophysical Activity Summary 29/2100Z to 30/2100Z: Geomagnetic field activity ranged from quiet to minor storm levels. Minor storm levels occurred globally during 29/2100 - 2400 UTC following a sustained period of southward IMF Bz (as measured by NASA's ACE spacecraft). Activity decreased to quiet to unsettled levels during 30/0000 - 1500 UTC, then increased to active levels for the rest of the period. An interplanetary shock passed the ACE spacecraft at 30/1848 UTC. The source for this shock may have been a CME that followed a long-duration M3/2n flare from Region 9636 at 28/0830 UTC. The greater than 10 MeV event that began at 24/1215 UTC ended at 30/1710 UTC. IIB. Geophysical Activity Forecast: Active geomagnetic conditions will be possible during 01 - 02 October due to recent CME activity. Field activity is expected to decrease to quiet to unsettled levels on 03 October. There will be a slight chance for a proton flare from Region 9628 or 9632 during the period. III. Event Probabilities 01 Oct-03 Oct Class M 80/75/70 Class X 25/20/10 Proton 20/15/10 PCAF yellow IV. Penticton 10.7 cm Flux Observed 30 Sep 236 Predicted 01 Oct-03 Oct 230/225/225 90 Day Mean 30 Sep 176 V. Geomagnetic A Indices Observed Afr/Ap 29 Sep 019/021 Estimated Afr/Ap 30 Sep 012/012 Predicted Afr/Ap 01 Oct-03 Oct 020/015-015/012-012/012 VI. Geomagnetic Activity Probabilities 01 Oct-03 Oct A. Middle Latitudes Active 40/40/30 Minor storm 20/20/10 Major-severe storm 10/10/01 B. High Latitudes Active 50/50/35 Minor storm 25/25/15 Major-severe storm 15/15/01