Viewing archive of Wednesday, 7 September 2005

Solar activity report

Report of Solar-Geophysical Activity 2005 Sep 07 2204 UTC
Prepared by the NOAA © SWPC and processed by

Joint USAF/NOAA Report of Solar and Geophysical Activity

SDF Number 250 Issued at 2200Z on 07 Sep 2005

IA. Analysis of Solar Active Regions and Activity from 06-2100Z to 07-2100Z

Solar activity increased to high levels this period as newly numbered Region 808 (S12E83) produced one of the largest solar flares of Cycle 23. An X17/3b white light flare erupted in this region at 07/1740Z. A large and fast CME was visible on the MK4 coronagraph at Mauna Loa. Intense centimetric radio bursts accompanied this flare, including a 27,000 sfu Tenflare. Type II (1860 km/s) and Type IV radio sweeps were also observed. This region also produced a very long duration M1 flare, which peaked at 06/2202Z. A fast and bright CME (1400 km/s) on LASCO imagery was observed with this event. The sunspot cluster associated with Region 808 is just now rotating into view, so an accurate assessment of its true size and complexity will have to wait. Region 808 is the return of old Region 798, which produced significant solar and geophysical activity during its last passage on the visible disk.
IB. Solar Activity Forecast
Solar activity is expected to be moderate to high. Region 808 is obviously a complex and moderate-large size sunspot group with great flare potential. Expect further major flares.
IIA. Geophysical Activity Summary 06-2100Z to 07-2100Z
The geomagnetic field was quiet to active. Today's powerful X17 flare produced a sudden disturbance in the geomagnetic field at 07/1725Z. This 82 nT magnetic crochet was one of the largest observed this Solar Cycle. A slow rise in the greater than 10 MeV protons at geosynchronous orbit began near issue time. The greater than 2 MeV electron flux at geosynchronous orbit reached high levels again today.
IIB. Geophysical Activity Forecast
The geomagnetic field is expected to continue at quiet to unsettled levels with isolated active periods. The CME activity associated with yesterday's long-duration M1 and today's X17 flares were not Earth directed. The greater than 10 MeV protons at geosynchronous orbit are slowly rising now and are expected to continue to do so. These protons will likely cross the 10 pfu threshold on 08 Sep.
III. Event Probabilities 08 Sep to 10 Sep
Class M 70%75%75%
Class X 30%30%30%
IV. Penticton 10.7 cm Flux
  Observed       07 Sep 100
  Predicted    08 Sep-10 Sep  110/120/120
  90 Day Mean        07 Sep 091
V. Geomagnetic A Indices
  Observed Afr/Ap 06 Sep  006/009
  Estimated     Afr/Ap 07 Sep  010/010
  Predicted     Afr/Ap 08 Sep-10 Sep  008/012-010/015-005/010
VI. Geomagnetic Activity Probabilities 08 Sep to 10 Sep
A. Middle Latitudes
Minor storm 05%05%05%
Major-severe storm 01%01%01%
B. High Latitudes
Minor storm 10%10%05%
Major-severe storm 01%01%01%

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