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NOAA Space Environment Center, Space Weather Forecast for October 28, 2003

Note text in boldface type below that forecasts impacts on Earth of the coronal mass ejection observed by the LASCO coronagraph.


: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  27/2100Zto 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