Joint USAF/NOAA Report of Solar and Geophysical Activity 20 September 2012

:Product: Report of Solar-Geophysical Activity
:Issued: 2012 Sep 20 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 264 Issued at 2200Z on 20 Sep 2012
IA. Analysis of Solar Active Regions and Activity from 19/2100Z
to 20/2100Z: Solar activity was at low levels. Region 1574 (S22W70)
produced a C1/Sf flare at 20/1139Z. Over the period, the region
grew from a simple unipolar spot to a 4 spot bipolar group. All
other spotted regions indicated little change. No 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 for the next
three days (21 – 23 September).
IIA. Geophysical Activity Summary 19/2100Z to 20/2100Z:
The geomagnetic field was at predominately quiet to unsettled levels
with a period of active conditions observed between 19/2100 – 2400Z.
The period began with wind speeds, as measured at the ACE
spacecraft, steady at 400 km/s while the Bz component of the
interplanetary magnetic field (IMF) was mostly south at about -10
nT. At about 19/2300Z, wind speed and temperature indicated slight
increases while IMF Bz began fluctuating between +8 to -6 nT. By
about 20/0100Z, the phi angle changed from a positive (away) to a
negative (toward) orientation. These changes were all indicative of
a co-rotating interaction region in advance of a coronal hole high
speed stream. By the end of the period, wind velocities were steady
at about 575 km/s while IMF Bz did not vary much beyond +/- 2 nT.
IIB. Geophysical Activity Forecast: The geomagnetic field is
expected to be at quiet to unsettled levels with isolated active
intervals for days one and two (21 – 22 September) as a coronal hole
high speed stream (CH HSS) remains geoeffective. By day three (23
September), mostly quiet to unsettled levels are expected as CH HSS
effects wane.
III. Event Probabilities 21 Sep-23 Sep
Class M 15/15/15
Class X 01/01/01
Proton 01/01/01
PCAF green
IV. Penticton 10.7 cm Flux
Observed 20 Sep 117
Predicted 21 Sep-23 Sep 115/115/120
90 Day Mean 20 Sep 122
V. Geomagnetic A Indices
Observed Afr/Ap 19 Sep 013/014
Estimated Afr/Ap 20 Sep 010/012
Predicted Afr/Ap 21 Sep-23 Sep 008/012-009/012-008/010
VI. Geomagnetic Activity Probabilities 21 Sep-23 Sep
A. Middle Latitudes
Active 30/30/20
Minor storm 05/05/01
Major-severe storm 01/01/01
B. High Latitudes
Active 35/35/25
Minor storm 10/10/05
Major-severe storm 01/01/01