Report of Solar-Geophysical Activity

Issued: 2011 Sep 27 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 270 Issued at 2200Z on 27 Sep 2011

IA.  Analysis of Solar Active Regions and Activity from  26/2100Z
to 27/2100Z:  Solar activity was low. Several C-class flares occurred
during the period from Region 1302 (N13E08). The largest of these
was a C6 flare at 27/2058Z.
IB.  Solar Activity Forecast:  Solar activity is expected to be low,
with a chance for M-class during the period (28-30 September). There
will also be a chance for an X-class flare.
IIA.  Geophysical Activity Summary 26/2100Z to 27/2100Z:
The geomagnetic field ranged from quiet to active levels. An isolated
period of major to severe storm levels were observed from
27/0000-0300Z. The greater than 10 MeV proton event began at
23/2300Z, reached a maximum of 35.7 pfu at 26/1155Z, and ended at
27/0430Z. Wind speeds reached 704 km/s at 26/2150Z and decreased to
512 km/s at 27/1703Z.
IIB.  Geophysical Activity Forecast:  The geomagnetic field is
expected to be at quiet to unsettled levels on day one (28
September). Quiet levels are expected on days two and three (29-30
September).
III.  Event Probabilities 28 Sep-30 Sep
Class M    40/40/40
Class X    25/25/25
Proton     10/10/10
PCAF       green
IV.  Penticton 10.7 cm Flux
Observed           27 Sep 139
Predicted   28 Sep-30 Sep  135/135/130
90 Day Mean        27 Sep 109
V.  Geomagnetic A Indices
Observed Afr/Ap 26 Sep  020/067
Estimated Afr/Ap 27 Sep  020/040
Predicted Afr/Ap 28 Sep-30 Sep  008/015-005/005-005/005
VI.  Geomagnetic Activity Probabilities 28 Sep-30 Sep
A.  Middle Latitudes
Active                15/05/05
Minor storm           01/01/01
Major-severe storm    01/01/01
B.  High Latitudes
Active                20/05/05
Minor storm           05/01/01
Major-severe storm    01/01/01