:Product: 20031028RSGA.txt
:Issued: 2003 Oct 28 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 301 Issued at 2200Z on 28 Oct 2003
IA.  Analysis of Solar Active Regions and Activity from  27/2100Z
to 28/2100Z:  Solar activity continues at high levels. Region 486
(S17E04) produced one of the largest flares of this solar cycle, an
X17/4B proton flare peaking at 28/1110Z.  This flare had intense
radio bursts including a 245 MhZ burst near 500,000 sfu and a
Tenflare of 13,000 pfu. A very fast (near 2000 km/s), earthward
directed full halo CME was observed on SOHO/LASCO imagery. Region
486, a beta-gamma-delta group with over 2100 millionths of white
light areal coverage, is now one of the largest and most complex
active regions of solar cycle 23. Region 484 (N03W68) maintains
considerable size and complexity as it approaches the west limb. It
produced occasional C-class activity and a low M-class flare at
28/1613Z. Region 488 (N08W04) continues its rapid growth and now
exceeds 800 millionths of coverage in a beta-gamma-delta
configuration. Frequent C-class flare activity was observed in this
region throughout the period. New region 493 (N09E05) was numbered
today.
IB.  Solar Activity Forecast:  Solar activity is expected to continue
at high levels. Region 486 in particular, has potential to produce
further major flare activity. An isolated major flare is also
possible from Regions 484 and 488.
IIA.  Geophysical Activity Summary 27/2100Z to 28/2100Z:
The geomagnetic field was quiet to active. A CME was observed to pass
the ACE spacecraft at around 0130Z. Solar wind speed rose to near
800 km/s, but Bz stayed northward, thwarting a significant
geomagnetic response. The X17 flare that occurred at 28/1110Z
produced proton events at greater than 10 and greater than 100 MeV
which remain in progress at this time. The greater than 100 MeV
event began at 28/1145Z with a maximum so far of 176 pfu. The
greater than 10 MeV proton event began at 28/1215Z with a maximum so
far of 6020 pfu. A polar cap absorption began at 28/1237Z and
remains in progress.
IIB.  Geophysical Activity Forecast:  The geomagnetic field is
expected to range from unsettled to potentially severe storming in
the next 24 to 48 hours. Today's X17 flare produced a large and fast
halo CME that will likely impact the Earth's magnetic field by
midday on day one.  Past events of this magnitude have almost always
produced severe storming. The storm is expected to continue through
at least the first half of day two. Unsettled to minor storm levels
are expected on day three.  The greater than 100 MeV proton event
is expected to end by day two. The greater than 10 MeV proton
event will likely persist through day three.
III.  Event Probabilities 29 Oct-31 Oct
Class M    90/90/90
Class X    50/50/50
Proton     99/99/75
PCAF       in progress
IV.  Penticton 10.7 cm Flux
Observed           28 Oct 274
Predicted   29 Oct-31 Oct  270/260/250
90 Day Mean        28 Oct 124
V.  Geomagnetic A Indices
Observed Afr/Ap 27 Oct  013/015
Estimated Afr/Ap 28 Oct  015/018
Predicted Afr/Ap 29 Oct-31 Oct  080/100-100/120-015/025
VI.  Geomagnetic Activity Probabilities 29 Oct-31 Oct
A.  Middle Latitudes
Active                15/15/50
Minor storm           25/25/15
Major-severe storm    60/60/05
B.  High Latitudes
Active                10/10/50
Minor storm           20/20/25
Major-severe storm    70/70/10