NOAA SEC Report of Solar-Geophysical Activity 27 Sep 2001
:Product: Report of Solar-Geophysical Activity :Issued: 2001 Sep 27 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 270 Issued at 2200Z on 27 Sep 2001 IA. Analysis of Solar Active Regions and Activity from 26/2100Z to 27/2100Z: Solar activity has been moderate for the past 24 hours. A long duration M1 x-ray event began at 0855 UTC, attained maximum at 1213 UTC, and ended at 1406 UTC. Although the source for the event was not certain, the most likely candidate appears to be a set of loops that were observed in EIT data just behind the northwest limb. It should be noted, however, that Region 9628 (S18W37) was undergoing frequent plage brightenings during the course of the event and may also have been a contributor. Region 9628 showed slight decay today, but continues to possess strong magnetic fields, including a delta near the center of the region. Region 9632 (S19W21) also continues to look impressive with a strong delta across an east-west inversion line. In spite of their size and complexity, none of the flares observed from these regions exceeded the subfaint level. Region 9634 (N12E11) showed some growth today as did Region 9637 (S14E32). Two new spot groups were assigned today: Region 9640 (N10E67) and Region 9641 (S14E77). Both appear to be quiet and stable. A CME was observed to enter the C2 field of view at 0854 UTC today over the southwest limb and appears to have characteristics of a partial halo event. IB. Solar Activity Forecast: Solar activity is expected to be moderate. There is a fair chance for an isolated major flare event during the next 3 days, with Regions 9628 and 9632 being the most likely sources. IIA. Geophysical Activity Summary 26/2100Z to 27/2100Z: The geomagnetic field was quiet to unsettled. The greater than 10 MeV proton event that began at 24/1215 UTC continued to decline today. Flux values had decreased to 270 pfu by forecast issue time. IIB. Geophysical Activity Forecast: The geomagnetic field is expected to be mostly unsettled for the next 24 hours. An increase to unsettled to slightly active is predicted for the 2nd and 3rd days as a response to a favorably positioned coronal hole. The greater than 10 MeV proton event is expected to end sometime late tomorrow or perhaps early on day two. III. Event Probabilities 28 Sep-30 Sep Class M 80/80/80 Class X 30/30/30 Proton 99/75/35 PCAF in progress IV. Penticton 10.7 cm Flux Observed 27 Sep 270 Predicted 28 Sep-30 Sep 265/260/260 90 Day Mean 27 Sep 172 V. Geomagnetic A Indices Observed Afr/Ap 26 Sep 013/024 Estimated Afr/Ap 27 Sep 010/010 Predicted Afr/Ap 28 Sep-30 Sep 010/010-015/015-015/018 VI. Geomagnetic Activity Probabilities 28 Sep-30 Sep A. Middle Latitudes Active 25/45/45 Minor storm 15/20/20 Major-severe storm 05/15/15 B. High Latitudes Active 25/45/45 Minor storm 15/20/20 Major-severe storm 05/15/15
