Viewing archive of Tuesday, 21 September 2004

Solar activity report

Report of Solar-Geophysical Activity 2004 Sep 21 2200 UTC
Prepared by the NOAA © SWPC and processed by

Joint USAF/NOAA Report of Solar and Geophysical Activity

SDF Number 265 Issued at 2200Z on 21 Sep 2004

IA. Analysis of Solar Active Regions and Activity from 20-2100Z to 21-2100Z

Solar activity was low. Region 672 (N04W86) produced a C7.5 flare at 0836Z. Region 672 will rotate around the west limb on 22 September. Region 673 (S13W04), the only other sunspot group on the visible disk, is in a slow decay phase. No new regions were numbered.
IB. Solar Activity Forecast
Solar activity is expected to be very low with a slight chance for C-class flares from Region 673 and 672 as it rotates around the west limb.
IIA. Geophysical Activity Summary 20-2100Z to 21-2100Z
The geomagnetic field was quiet to unsettled with an isolated active period between 0300Z to 0600Z. The active conditions followed a period of southward IMF Bz. Solar wind plasma and magnetic field measurements indicate the presence of a weak coronal hole stream.
IIB. Geophysical Activity Forecast
The geomagnetic field is expected to be quiet to active with a possibility of reaching minor storm levels on 22 September. Active to minor storm periods are possible on the 22nd due to a weak high speed solar wind stream and the expected impact of a CME that occurred late on 19 September. Levels are expected to return to quiet to unsettled with isolated active periods on 23-24 September.
III. Event Probabilities 22 Sep to 24 Sep
Class M05%05%05%
Class X01%01%01%
IV. Penticton 10.7 cm Flux
  Observed       21 Sep 095
  Predicted   22 Sep-24 Sep  090/090/090
  90 Day Mean        21 Sep 112
V. Geomagnetic A Indices
  Observed Afr/Ap 20 Sep  008/013
  Estimated     Afr/Ap 21 Sep  008/010
  Predicted    Afr/Ap 22 Sep-24 Sep  020/025-010/015-008/010
VI. Geomagnetic Activity Probabilities 22 Sep to 24 Sep
A. Middle Latitudes
Minor storm15%10%05%
Major-severe storm05%05%01%
B. High Latitudes
Minor storm25%20%10%
Major-severe storm10%10%01%

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