Status Report

NOAA SEC Report of Solar-Geophysical Activity 27 Sep 2001

By SpaceRef Editor
September 27, 2001
Filed under , ,
: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

SpaceRef staff editor.