Status Report

Joint USAF/NOAA Report of Solar and Geophysical Activity 24 Aug 2005

By SpaceRef Editor
August 25, 2005
Filed under , ,

Prepared jointly by the U.S. Dept. of Commerce, NOAA,
Space Environment Center and the U.S. Air Force.
Updated 2005 Aug 24 2202 UTC

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-27 Aug

  • Class M 50/30/20
  • Class X 05/01/01
  • Proton 90/20/05
  • PCAF in 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-27 Aug

A. Middle Latitudes

  • Active 35/25/20
  • Minor storm 35/20/10
  • Major-severe storm 15/10/05

B. High Latitudes

  • Active 35/30/15
  • Minor storm 25/15/10
  • Major-severe storm 20/10/05

SpaceRef staff editor.