Status Report

Joint USAF/NOAA Report of Solar and Geophysical Activity 27 Jul 2004

By SpaceRef Editor
July 27, 2004
Filed under , ,

Prepared jointly by the U.S. Dept. of Commerce, NOAA,
Space Environment Center and the U.S. Air Force.

Updated 2004 Jul 27 2200 UTC

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

SpaceRef staff editor.