Joint USAF/NOAA Report of Solar and Geophysical Activity 25 September 2011
:Product: Report of Solar-Geophysical Activity
:Issued: 2011 Sep 25 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 268 Issued at 2200Z on 25 Sep 2011
IA. Analysis of Solar Active Regions and Activity from 24/2100Z
to 25/2100Z: Solar activity was high. Regions 1302 (N12E36) and
1303 (S28W79) each produced three M-class flares. The largest was
an M7/2N at 25/0450Z. A partial halo CME was observed at 24/1936Z
in LASCO C2 imagery which was likely associated with the M3 flare
from Region 1302 that occurred at 24/1921Z. The event had an
associated Type II (1369 km/s) and an approximate plane of sky speed
of 800 km/s using LASCO C3 imagery. Two more CMEs were observed at
25/0236Z and 25/0312Z off the Southwest limb in LASCO C2 imagery,
however they are not expected to be geoeffective.
IB. Solar Activity Forecast: Solar activity is expected to continue
at high levels with a chance for isolated X-class flares from Region
1302.
IIA. Geophysical Activity Summary 24/2100Z to 25/2100Z:
The geomagnetic field was mostly quiet. A sudden impulse (SI) was
observed at the ACE spacecraft at approximately 25/1106Z. The IMF
Bt increased from approximately 5 nT to 10 nT while the field
density increased to around 7 p/cc. The greater than 10 MeV protons
event that began at 23/2255Z reached a peak of 27.3 PFUs at 25/2030Z
and continues to remain above the 10 PFU threshold.
IIB. Geophysical Activity Forecast: The geomagnetic field is
expected to be at unsettled to minor storm conditions with major
storm periods possible at high latitudes on day 1 (26 September) due
to activity from the CME associated with the M7 flare that occurred
at 24/1320Z. Mostly unsettled conditions are expected on days 2-3
(27-28 September) due to continued activity from the CME as well as
a possible glancing blow from a weak CME on day 3. The greater than
10 MeV proton flux is expected to continue to remain above threshold
for the next three days.
III. Event Probabilities 26 Sep-28 Sep
Class M 80/80/80
Class X 40/40/40
Proton 99/99/80
PCAF yellow
IV. Penticton 10.7 cm Flux
Observed 25 Sep 169
Predicted 26 Sep-28 Sep 170/170/170
90 Day Mean 25 Sep 108
V. Geomagnetic A Indices
Observed Afr/Ap 24 Sep 003/004
Estimated Afr/Ap 25 Sep 007/007
Predicted Afr/Ap 26 Sep-28 Sep 025/030-012/012-008/015
VI. Geomagnetic Activity Probabilities 26 Sep-28 Sep
A. Middle Latitudes
Active 45/30/15
Minor storm 20/15/05
Major-severe storm 10/05/01
B. High Latitudes
Active 45/30/35
Minor storm 25/15/15
Major-severe storm 15/05/05
