:Product: 0926RSGA.txt
:Issued: 2011 Sep 26 2200 UTC
# Prepared jointly by the U.S. Dept. of Commerce, NOAA,
# Space Weather Prediction Center and the U.S. Air Force.
#
Joint USAF/NOAA Report of Solar and Geophysical Activity
SDF Number 269 Issued at 2200Z on 26 Sep 2011
IA.  Analysis of Solar Active Regions and Activity from  25/2100Z
to 26/2100Z:  Solar activity has been at moderate levels for the past
24 hours. Region 1302 (N13E23) produced the largest event of the
period, a M2 x-ray flare at 1446Z. Region 1301 (N17W23) and Region
1303 (S28W90) also produced several low level C-class events.
IB.  Solar Activity Forecast:  Solar activity is expected to remain
at moderate levels on day one (27 September). Low to moderate levels
are expected on day two (28 September) and predominantly low levels
are expected on day three (29 September). Region 1302 remains the
most active Region on the disk but has only produced one M-class
event over the past 24 hours.
IIA.  Geophysical Activity Summary 25/2100Z to 26/2100Z:
The geomagnetic field has been at major storm levels for the past 24
hours. A CME, observed leaving the solar disk on 24 September,
arrived at Earth on 26/1237Z. Indicating the arrival of the CME, a
45 nT sudden impulse was observed by the Boulder magnetometer. As
the CME progressed, measurements by the ACE spacecraft showed the
total IMF reaching a peak of 33 nT, with the negative (Southward
Component, Bz) reaching a maximum of-31 nT. Solar wind speeds
increased from around 350 km/s to 650 km/s. During the CME passage,
both GOES 13 and GOES 15 spacecraft showed clear magnetopause
crossings. The greater than 10 MeV proton event, that began at
23/2255Z, reached up to 35.7 pfu at 26/1115Z, and continues to
remain above the 10 pfu threshold.
IIB.  Geophysical Activity Forecast:  The geomagnetic field is
expected to be at unsettled to active levels for the next two days
(27-28 September) with a slight chance for minor storm levels, due
to the trailing effects of the latest CME and the possible arrival
of a second CME. A return to predominately quiet levels is expected
on day three (29 September).
III.  Event Probabilities 27 Sep-29 Sep
Class M    80/40/30
Class X    40/10/05
Proton     99/30/10
PCAF       yellow
IV.  Penticton 10.7 cm Flux
Observed           26 Sep 148
Predicted   27 Sep-29 Sep  145/145/140
90 Day Mean        26 Sep 108
V.  Geomagnetic A Indices
Observed Afr/Ap 25 Sep  004/004
Estimated Afr/Ap 26 Sep  027/060
Predicted Afr/Ap 27 Sep-29 Sep  012/010-010/015-005/005
VI.  Geomagnetic Activity Probabilities 27 Sep-29 Sep
A.  Middle Latitudes
Active                30/15/05
Minor storm           15/05/01
Major-severe storm    05/01/01
B.  High Latitudes
Active                35/20/10
Minor storm           10/10/01
Major-severe storm    05/01/01