Viewing archive of Thursday, 25 August 2011

Solar activity report

Report of Solar-Geophysical Activity 2011 Aug 25 2200 UTC
Prepared by the NOAA © SWPC and processed by

Joint USAF/NOAA Report of Solar and Geophysical Activity

SDF Number 237 Issued at 2200Z on 25 Aug 2011

IA. Analysis of Solar Active Regions and Activity from 24-2100Z to 25-2100Z

Solar activity was at very low levels. Region 1271 (N17W56) decayed in area and spot count, but developed a Delta magnetic configuration in the large leader spot. The region produced numerous low-level B-class events. Three new regions were numbered during the period. In the western hemisphere, new Region 1278 (N16W40) emerged as a simple 4-spot bi-polar group. On the eastern limb, new Region 1277 (N17E62) and new Region 1279 (N14E75) both rotated onto the disk as large, uni-polar H-type groups. Region 1277 produced a B9 x-ray event at 25/0702Z while Region 1279 produced another B9 x-ray event at 25/1652Z. The SOHO LASCO satellite observed a slow-moving CME off the east limb, first observed in C2 imagery at 25/0856Z with an estimated plane-of-sky speed of 420 km/s. This CME does not appear to have an Earthward directed component.
IB. Solar Activity Forecast
Solar activity is expected to be low with a slight chance for an M-class event all three days (26 - 28 August).
IIA. Geophysical Activity Summary 24-2100Z to 25-2100Z
The geomagnetic field was at quiet levels. Observations from the ACE spacecraft indicated a steady decline in solar wind velocity during the period from about 500 km/s to near 400 km/s. The Bz component of the interplanetary magnetic field did not vary much beyond +/- 4 nT while the phi angle remained negative (toward) throughout the period.
IIB. Geophysical Activity Forecast
The geomagnetic field is expected to remain at quiet levels for days one and two (26 - 27 August). By day three (28 August), activity levels are expected to increase to quiet to unsettled, with isolated active periods, due to a geoeffective, recurrent coronal hole high speed stream.
III. Event Probabilities 26 Aug to 28 Aug
Class M10%10%10%
Class X01%01%01%
IV. Penticton 10.7 cm Flux
  Observed       25 Aug 104
  Predicted   26 Aug-28 Aug  110/115/115
  90 Day Mean        25 Aug 097
V. Geomagnetic A Indices
  Observed Afr/Ap 24 Aug  005/006
  Estimated     Afr/Ap 25 Aug  005/005
  Predicted    Afr/Ap 26 Aug-28 Aug  005/005-005/005-007/010
VI. Geomagnetic Activity Probabilities 26 Aug to 28 Aug
A. Middle Latitudes
Minor storm01%01%05%
Major-severe storm01%01%01%
B. High Latitudes
Minor storm01%01%15%
Major-severe storm01%01%01%

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