Joint USAF/NOAA Report of Solar and Geophysical Activity 24 October 2011

:Product: Report of Solar-Geophysical Activity
:Issued: 2011 Oct 24 2244 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 297 Issued at 2200Z on 24 Oct 2011
IA. Analysis of Solar Active Regions and Activity from 23/2100Z
to 24/2100Z: Solar activity was low. Region 1330 (N08E45) produced a
C1 x-ray event at 23/2237Z. The region continued to evolve as it
rotated more fully on the disk. It grew in both area coverage and
spot count and developed a beta-gamma magnetic configuration. The
other significant region of interest, Region 1324 (N12W13), was
quiet and stable during the period. New Region 1332 (N32E78)
rotated onto the disk as an H-type spot.
IB. Solar Activity Forecast: Solar activity is expected to be low
with a slight chance for isolated M-class activity. Regions 1324
(N12W13) and 1330 (N08E45) are the most likely for moderate level
activity.
IIA. Geophysical Activity Summary 23/2100Z to 24/2100Z:
The geomagnetic field was at mostly quiet with a single active period
observed between 24/1800 – 2100Z. The ACE spacecraft observed an
interplanetary shock passage at 24/1748Z with a subsequent sudden
impulse of 13 nT observed at the Boulder magnetometer at 24/1832Z.
Observations at ACE revealed increases in temperature, density and
wind speed while the Bz component of the interplanetary magnetic
field (IMF) decreased southward to -20 nT for a brief period. IMF
Bt reached 20 nT. Wind velocities increased from a steady 350 km/s
to 525 km/s and remained so through the end of the period. This
mostly likely was the arrival of a CME that occurred at 22/0058Z in
association with an eruptive filament. The greater than 10 MeV
proton event that began at 23/1500Z ended at 23/1605Z. A peak flux
of 13 pfu was reached at 23/1535Z. Earlier in the period, another,
weaker shock passage was observed in the ACE solar wind data at
23/2320Z. This was most likely the result of a glancing blow from a
CME associated with an M1.6 x-ray event observed of the NW limb at
20/0325Z .
IIB. Geophysical Activity Forecast: The geomagnetic field is
expected to be at quiet to unsettled levels, with isolated active
periods on day one (25 October), due to lingering effects of the 24
October CME passage. By day two (26 October), the field is expected
to mostly quiet with isolated unsettled periods returning to mostly
quiet on day three (27 October).
III. Event Probabilities 25 Oct-27 Oct
Class M 20/20/20
Class X 01/01/01
Proton 01/01/01
PCAF Green
IV. Penticton 10.7 cm Flux
Observed 24 Oct 145
Predicted 25 Oct-27 Oct 145/140/140
90 Day Mean 24 Oct 123
V. Geomagnetic A Indices
Observed Afr/Ap 23 Oct 002/003
Estimated Afr/Ap 24 Oct 009/010
Predicted Afr/Ap 25 Oct-27 Oct 010/012-007/008-005/007
VI. Geomagnetic Activity Probabilities 25 Oct-27 Oct
A. Middle Latitudes
Active 40/30/05
Minor storm 05/05/01
Major-severe storm 01/01/01
B. High Latitudes
Active 50/40/20
Minor storm 15/10/05
Major-severe storm 01/01/01