Viewing archive of Thursday, 27 September 2001

Solar activity report

Report of Solar-Geophysical Activity 2001 Sep 27 2200 UTC
Prepared by the NOAA © SWPC and processed by

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 to 30 Sep
Class M80%80%80%
Class X30%30%30%
PCAFin 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 to 30 Sep
A. Middle Latitudes
Minor storm15%20%20%
Major-severe storm05%15%15%
B. High Latitudes
Minor storm15%20%20%
Major-severe storm05%15%15%

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