Joint USAF/NOAA Report of Solar and Geophysical Activity 25 October 2011

:Product: Report of Solar-Geophysical Activity
:Issued: 2011 Oct 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 298 Issued at 2200Z on 25 Oct 2011
IA. Analysis of Solar Active Regions and Activity from 24/2100Z
to 25/2100Z: Solar activity was at low levels due to a single C1
x-ray event from Region 1330 (N08E31). Regions 1325 (N15E03), 1327
(S21W54) and 1330) indicated some decay in area. The remaining
regions were unchanged.
IB. Solar Activity Forecast: Solar activity is expected to be low
with a slight chance for M-class activity all three days (26 – 28
October). Regions 1324 (N12W26) and 1330 (N08E29) are the most
likely to produce moderate level activity.
IIA. Geophysical Activity Summary 24/2100Z to 25/2100Z:
The geomagnetic field ranged from quiet to severe storm levels. The
period began with unsettled to minor storm levels. By 25/0000Z,
minor to major storm levels, with high latitude severe storm levels,
were observed. From 25/0300Z – 0900Z, active to major storm levels
predominated followed by quiet to active levels for the remainder of
the period. This increase in activity was likely associated with
effects following the arrival of CME activity, first observed on 22
October. Following the interplanetary shock observed at the ACE
spacecraft on 24/1748Z. ACE registered increases in wind speed,
temperature and density. Solar wind velocities increased from a
steady 350 km/s to about 525 km/s, and remained at that speed
throughout the period. The interplanetary magnetic field (IMF) Bt
increased to above 20 nT from about 24/2000Z through 25/1300Z and
gradually decreased to about 8 nT by the end of the period. The Bz
component of the IMF reached southward values of -20 nT from about
24/2000Z through 25/0000Z. The remainder of the period observed
mostly northward Bz.
IIB. Geophysical Activity Forecast: The geomagnetic field is
expected to be at quiet to unsettled levels, with isolated active
periods on day one (26 October), due to lingering effects from the
CME that impacted Earth on 24 October. Mostly quiet conditions are
expected on day two (27 October). By day three (28 October), quiet
to unsettled levels are expected due to effects from a recurrent
coronal hole high speed stream.
III. Event Probabilities 26 Oct-28 Oct
Class M 20/20/20
Class X 01/01/01
Proton 01/01/01
PCAF Green
IV. Penticton 10.7 cm Flux
Observed 25 Oct 139
Predicted 26 Oct-28 Oct 140/140/135
90 Day Mean 25 Oct 123
V. Geomagnetic A Indices
Observed Afr/Ap 24 Oct 016/023
Estimated Afr/Ap 25 Oct 028/040
Predicted Afr/Ap 26 Oct-28 Oct 007/012-005/005-007/007
VI. Geomagnetic Activity Probabilities 26 Oct-28 Oct
A. Middle Latitudes
Active 15/05/15
Minor storm 05/01/05
Major-severe storm 01/01/01
B. High Latitudes
Active 30/10/20
Minor storm 15/05/10
Major-severe storm 01/01/01