:Product: 20040727RSGA.txt
:Issued: 2004 Jul 27 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 209 Issued at 2200Z on 27 Jul 2004
IA.  Analysis of Solar Active Regions and Activity from  26/2100Z
to 27/2100Z:  Solar activity was moderate. Region 652 (N07W62)
produced three M1 flares this period. Region 652 continues to slowly
decay as it approaches the west limb. It still maintains
considerable size and a complex delta configuration. No other
significant changes were observed on the disk or limb.
IB.  Solar Activity Forecast:  Solar activity is expected to be
moderate. Continued M-class activity is expected from Region 652 and
there is a slight chance for a major flare.
IIA.  Geophysical Activity Summary 26/2100Z to 27/2100Z:
The geomagnetic field ranged from unsettled to severe storming. A
strong sudden impulse (SI) of 95 Nt was observed on the Boulder
magnetometer at 26/2228Z. This SI followed the very fast (~31 hours)
transit of the full halo CME associated with the long duration M1
flare on 25/1514Z. Solar wind speed increased from the already
elevated levels near 600 km/s to over 1050 km/s. After approximately
four hours of fluctuating between  -15 and +15 nT, the IMF Bz
rotated strong southward and ranged from -15 to -25 nT for about 15
hours. The fast solar wind speed and southward Bz combined to
produce severe geomagnetic storm levels at all latitudes from
27/0000Z to 27/1500Z. Solar wind speed was still near 800 km/s by
the end of the period and the disturbance had declined to minor
storm levels. The greater than 10 MeV proton event that began on
25/1855Z is still in progress. A rapid, short-lived increase in the
greater than 10 MeV protons to 2,090 pfu occurred with the shock
passage. Protons quickly declined and were straddling the 10 pfu
alert threshold by the end of the period. The greater than 2 MeV
electrons at geosynchronous orbit were at high levels.
IIB.  Geophysical Activity Forecast:  The geomagnetic field is
expected to range from quiet to major storm levels. The most
disturbed periods are expected during the first half of day one as
the current major disturbance subsides. Mostly quiet to unsettled
conditions are expected on 29 - 30 July.
III.  Event Probabilities 28 Jul-30 Jul
Class M    55/40/10
Class X    10/05/05
Proton     99/10/05
PCAF       yellow
IV.  Penticton 10.7 cm Flux
Observed           27 Jul 118
Predicted   28 Jul-30 Jul  110/105/090
90 Day Mean        27 Jul 106
V.  Geomagnetic A Indices
Observed Afr/Ap 26 Jul  026/031
Estimated Afr/Ap 27 Jul  120/180
Predicted Afr/Ap 28 Jul-30 Jul  020/025-010/015-008/010
VI.  Geomagnetic Activity Probabilities 28 Jul-30 Jul
A.  Middle Latitudes
Active                50/35/20
Minor storm           25/05/05
Major-severe storm    15/01/01
B.  High Latitudes
Active                50/40/20
Minor storm           30/10/05
Major-severe storm    20/05/01