NOAA SEC Report of Solar-Geophysical Activity 26 Sep 2001
:Product: Report of Solar-Geophysical Activity :Issued: 2001 Sep 26 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 269 Issued at 2200Z on 26 Sep 2001 IA. Analysis of Solar Active Regions and Activity from 25/2100Z to 26/2100Z: Solar activity has been moderate. Region 9628 (S18W26) produced today's only M-class event, an M1 at 0258 UTC. The region has shown a slight decline and simplification relative to yesterday, but continues to be the largest on the disk and continues to have strong, complex magnetic fields. Region 9632 (S19W08) also continues to be impressive but produced only low-level C-class events. Region 9636 (N13E40) appears to be growing slowly and managed to produce a couple subflares. New Region 9639 (N04E36) was assigned today and is a simple beta-type sunspot group. IB. Solar Activity Forecast: Solar activity is expected to be moderate. There is a fair chance, however, for an isolated major flare event or proton producing event from either of Regions 9632 or 9628. IIA. Geophysical Activity Summary 25/2100Z to 26/2100Z: The geomagnetic field has ranged from quiet to major storm levels during the past 24 hours. Following yesterday's sudden storm commencement at 2025 UTC, the geomagnetic field became disturbed, and attained major storm levels between 2100-2400 UTC. Conditions declined slightly from 0000-1200 UTC, with active to minor storm levels predominating. Activity was quiet to unsettled for the remainder of the period. The greater than 10 MeV proton event continues in progress. A maximum flux of 12900 pfu was observed at 25/2235 UTC, after which the flux levels have been steadily declining. The greater than 100 MeV proton event that began at 1440 UTC on the 24th attained maximum of 31 PFU at 25/0755 UTC and ended at 26/1940 UTC. IIB. Geophysical Activity Forecast: The geomagnetic field is expected to be mostly unsettled during the next three days. There is a chance for some active periods during the next 12 hours due to persistence. Unsettled levels should dominate on the second day. There is a chance for some active periods on the third day due to the favorable position of a solar coronal hole. The greater than 10 MeV proton event is expected to continue for the next 42-48 hours. III. Event Probabilities 27 Sep-29 Sep Class M 80/80/80 Class X 30/30/30 Proton 99/90/50 PCAF in progress IV. Penticton 10.7 cm Flux Observed 26 Sep 283 Predicted 27 Sep-29 Sep 280/275/275 90 Day Mean 26 Sep 171 V. Geomagnetic A Indices Observed Afr/Ap 25 Sep 017/018 Estimated Afr/Ap 26 Sep 022/025 Predicted Afr/Ap 27 Sep-29 Sep 015/010-010/010-015/015 VI. Geomagnetic Activity Probabilities 27 Sep-29 Sep A. Middle Latitudes Active 35/30/35 Minor storm 20/15/25 Major-severe storm 10/05/10 B. High Latitudes Active 30/30/30 Minor storm 20/15/30 Major-severe storm 15/05/20
