Joint USAF/NOAA Report of Solar and Geophysical Activity 28 September 2012
:Product: Report of Solar-Geophysical Activity
:Issued: 2012 Sep 28 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 272 Issued at 2200Z on 28 Sep 2012
IA. Analysis of Solar Active Regions and Activity from 27/2100Z
to 28/2100Z: Solar activity was at low levels. Region 1577 (N08W41)
produced a long duration C3/1f flare at 27/2357Z. The event began
with a filament eruption located northwest of and adjacent to the
region with a subsequent dual ribbon flare. Associated with this
event was an Earth-directed, asymmetric, full-halo CME first visible
in SOHO LASCO C2 and C3 imagery at 28/0018Z and 28/0030Z,
respectively. The plane-of-sky speed through both fields averaged
1034 km/s with a computed radial velocity of 872 km/s. Little
change was observed for the remainder of the disk and limb. No
other Earth-directed CMEs were observed.
IB. Solar Activity Forecast: Solar activity is expected to be at
low levels with a slight chance for M-class activity all three days
of the forecast period (29 – 30 September and 01 October).
IIA. Geophysical Activity Summary 27/2100Z to 28/2100Z:
The geomagnetic field was at quiet levels. ACE satellite
measurements indicated a steady decline in wind velocity from about
400 km/s to near 325 km/s while the Bz component of the
interplanetary magnetic field did not vary much beyond +/- 2 nT.
The greater than 10 MeV proton flux at geosynchronous orbit exceeded
threshold at 28/0300Z, reached a maximum of 28 pfu at 28/0445Z and
decayed below threshold at 28/1040Z. At the time of this report,
flux levels were still elevated at about 5 pfu. This event was
believed to be associated with the C3/1f flare observed late on 27
September.
IIB. Geophysical Activity Forecast: Geomagnetic field activity is
expected to be at predominately quiet levels on day one (29
September) and through midday on day two (30 September). By late
on day two, active levels with a chance for minor to major storm
periods are expected due to the arrival of the Earth-directed CME
observed early on 28 September. On day three (01 October),
continued minor to major storm conditions are expected early in the
day, decreasing to mostly quiet to unsettled levels with isolated
active periods as effects from the CME wane.
III. Event Probabilities 29 Sep-01 Oct
Class M 10/10/10
Class X 01/01/01
Proton 01/01/01
PCAF green
IV. Penticton 10.7 cm Flux
Observed 28 Sep 138
Predicted 29 Sep-01 Oct 135/135/130
90 Day Mean 28 Sep 125
V. Geomagnetic A Indices
Observed Afr/Ap 27 Sep 003/004
Estimated Afr/Ap 28 Sep 002/003
Predicted Afr/Ap 29 Sep-01 Oct 004/005-018/035-018/025
VI. Geomagnetic Activity Probabilities 29 Sep-01 Oct
A. Middle Latitudes
Active 05/35/35
Minor storm 01/25/30
Major-severe storm 01/05/05
B. High Latitudes
Active 15/10/10
Minor storm 15/25/25
Major-severe storm 05/50/65
