Joint USAF/NOAA Report of Solar and Geophysical Activity 9 September 2011

:Product: Report of Solar-Geophysical Activity
:Issued: 2011 Sep 09 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 252 Issued at 2200Z on 09 Sep 2011
IA. Analysis of Solar Active Regions and Activity from 08/2100Z
to 09/2100Z: Solar activity has been moderate. Region 1283 (N17W55)
produced two M-class flares. The first was an M2/1n at 09/0611Z with
an associated Type II radio sweep (estimated velocity 717 km/sec)
and a non-geoeffective CME. The second was an M1/1f at 09/1249Z.
Region 1283 showed penumbral and trailer spot decay. Region 1289
(N22E37) developed a trailer spot with penumbra. New Region 1290
(S15E29) was numbered during the period.
IB. Solar Activity Forecast: Solar activity is expected to be
moderate during the period (10 – 12 September) with a slight chance
for another X-class flare from Region 1283.
IIA. Geophysical Activity Summary 08/2100Z to 09/2100Z:
Geomagnetic field activity began the period at quiet levels then
increased to active to major storm levels after 09/1245Z. An
isolated severe storm period was observed from 09/1500 – 1800Z. Two
sudden impulses (SI) were observed at 09/1243Z and 09/1250Z (16nT
and 28nT respectively, as measured by the Boulder USGS
magnetometer). At 09/1150Z, ACE data indicated an interplanetary
shock arrival preceding the Boulder SIs. Bt reached up to 25nT, Bz
dropped to -23nT, density spiked up to 35p/cc, wind speeds peaked at
602km/s, and temperature increased. Activity was due to combined
CMEs associated with 06 – 07 September major flare activity. The
greater than 2 MeV electron flux at geosynchronous orbit reached
high levels during the period.
IIB. Geophysical Activity Forecast: The geomagnetic field is
expected to be active on day 1 (10 September) due to continuing CME
effects. Activity is expected to decrease on day 2 (11 September) to
unsettled levels with a chance for active periods as CME effects
subside, but a recurrent coronal hole high speed stream (CH HSS)
will become geoeffective. Day 3 (12 September) unsettled activity is
expected to continue under the effects of the CH HSS. There will be
a slight chance for a greater than 10 MeV proton event at
geosynchronous orbit during the period.
III. Event Probabilities 10 Sep-12 Sep
Class M 70/65/60
Class X 20/15/10
Proton 15/10/05
PCAF Green
IV. Penticton 10.7 cm Flux
Observed 09 Sep 112
Predicted 10 Sep-12 Sep 110/110/110
90 Day Mean 09 Sep 099
V. Geomagnetic A Indices
Observed Afr/Ap 08 Sep 002/004
Estimated Afr/Ap 09 Sep 018/035
Predicted Afr/Ap 10 Sep-12 Sep 020/022-012/015-008/008
VI. Geomagnetic Activity Probabilities 10 Sep-12 Sep
A. Middle Latitudes
Active 30/25/20
Minor storm 25/10/05
Major-severe storm 05/01/01
B. High Latitudes
Active 40/30/25
Minor storm 30/15/10
Major-severe storm 10/01/01