Viewing archive of Wednesday, 24 August 2005

Solar activity report

Report of Solar-Geophysical Activity 2005 Aug 24 2203 UTC
Prepared by the NOAA © SWPC and processed by

Joint USAF/NOAA Report of Solar and Geophysical Activity

SDF Number 236 Issued at 2200Z on 24 Aug 2005

IA. Analysis of Solar Active Regions and Activity from 23-2100Z to 24-2100Z

Solar activity was low during the past 24 hours. Today's activity consisted of a few C-class events. The largest was a C4 at 0706 UTC from Region 798 (S11W90) which is rotating off the visible disk. Region 800 (N17W21) and newly numbered Region 803 (N12E78) also contributed to the activity. New Region 802 (S12E14) emerged on the disk today as a small, simple H-type group.
IB. Solar Activity Forecast
Solar activity is expected to be mostly low, but there is a fair chance for an isolated M-class event from Region 798 during the next 24 hours (25 August). Probabilities will decline for 26-27 August but there will still be a slight chance for an isolated M-class event from Region 800 or Region 803.
IIA. Geophysical Activity Summary 23-2100Z to 24-2100Z
The geomagnetic field ranged from quiet to severe storm levels. An initially quiet to unsettled field became disturbed after a series of two shocks and transient flow. The first shock was seen at ACE at 0539 UTC and was followed by a sudden impulse at 0612 UTC and minor storm level activity. The second shock was observed at 0828 UTC and was followed by about 6 hours of major to severe storm level activity, which was driven by high velocity and very strongly negative interplanetary magnetic field component Bz (which reached about -56 nT). Activity declined to minor storm levels after 1500 UTC and remained there through the end of the period. The solar wind remains elevated but is slowly declining; Bz turned mostly northwards and substantially weakened although the total solar wind magnetic field remains high (about 20 nT). The solar wind signatures are most consistent with the successive arrivals of CMEs associated with the M2 of 22/0133 UTC and the M5 of 22/1727 UTC. The greater than 10 MeV proton event that began at 22/2040 UTC and reached a maximum of 330 PFU at 23/1045 UTC continues in progress with flux of about 19 PFU at the end of the period.
IIB. Geophysical Activity Forecast
The geomagnetic field is expected to be at active to minor storm levels with a chance for isolated major storm intervals for the next 24 hours (25 August) as the current disturbance is likely to persist. In addition, a favorably positioned coronal hole is likely to keep the solar wind velocity elevated in this flow behind the CMEs. There is also a chance for a glancing blow contribution to activity from the M2/CME of 23/1444 UTC. Conditions should subside to unsettled to active for 26 August and should be mostly unsettled by 27 August. The greater than 10 MeV proton event will probably end sometime on 25 August.
III. Event Probabilities 25 Aug to 27 Aug
Class M50%30%20%
Class X05%01%01%
PCAFin progress
IV. Penticton 10.7 cm Flux
  Observed       24 Aug 099
  Predicted   25 Aug-27 Aug  100/095/095
  90 Day Mean        24 Aug 094
V. Geomagnetic A Indices
  Observed Afr/Ap 23 Aug  007/009
  Estimated     Afr/Ap 24 Aug  050/125
  Predicted    Afr/Ap 25 Aug-27 Aug  025/040-015/020-010/008
VI. Geomagnetic Activity Probabilities 25 Aug to 27 Aug
A. Middle Latitudes
Minor storm35%20%10%
Major-severe storm15%10%05%
B. High Latitudes
Minor storm25%15%10%
Major-severe storm20%10%05%

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