Product: Weekly Highlights and Forecasts
:Issued: 2011 Oct 25 1916 UTC
# Prepared by the US Dept. of Commerce, NOAA, Space Weather Prediction
Center
# Product description and SWPC contact on the Web
# http://www.swpc.noaa.gov/weekly.html
#
# Weekly Highlights and Forecasts
#
Highlights of Solar and Geomagnetic Activity
17 - 23 October 2011

Solar activity was low to moderate. Early in the period, solar
activity was at low levels with a majority of the C-class activity
from Regions 1319 (N=10, L=051, class/area Eki/420 on 17 October)
and 1324 (N11, L=305, class/area Ekc/360 on 20 October). Low level
C-class activity was observed until early on 20 October when an M1
x-ray event occurred at 20/0325Z from an area on the west limb. This
event most likely originated from Region 1318 (N20, L=096,
class/area Dso/50 on 13 October). M-class activity continued during
21 and 22 October with an M1 x-ray event at 21/1300Z from Region
1319 and a M1/Sf long duration flare at 22/1110Z from Region 1314
(N25, L=058, class/area Cho/370 on 12 October). The 21 October
M-flare had associated Type II (789 km/s) and Type IV radio sweeps,
but no Earth-directed CME was detected. The 22 October M-flare had
an associated CME with a mostly northward directed component with an
approximate plane-of-sky speed of 600 km/s measured in STEREO A
COR2. LASCO C2 and C3 imagery observed a partial halo CME with a
maximum plane-of-sky speed of 1000 km/s in its northernmost edge. A
large filament eruption was also observed in SDO/AIA imagery in the
Northwest quadrant of the solar disk starting at 22/0058Z. An
associated CME was observed with a slight Earth-directed component
with an approximate speed of 500 km/s. Activity returned to low
levels on the last day of the period.

The greater than 100 MeV proton flux at geosynchronous orbit
remained below threshold levels the entire period. A greater than 10
MeV proton event began at 23/1500Z in response to the M1/Sf
long-duration flare observed midday on 22 October. The event peaked
at 13pfu at 23/1535Z and ended at 23/1605Z.

The greater than 2 MeV electron flux at geosynchronous orbit was at
normal levels the entire period.

The geomagnetic field was mostly quiet during the summary period. On
the last day of the summary period, a weak shock passage was
observed in the ACE solar wind data at 23/2320Z, but the geomagnetic
field remained quiet. A glancing blow from a CME associated with an
M1 x-ray event observed near the NW limb at 20/0325Z was the
suspected source of the shock.

Forecast of Solar and Geomagnetic Activity
26 October - 21 November 2011

Solar activity is expected to be at predominantly low levels during
the forecast period. There will be a slight chance for M-class
activity during 26 October - 03 November. M-class activity increases
from a slight chance to a chance during 04 - 17 November, with a
slight chance for X-class activity from 04 - 17 November, due to the
return of old active Regions 1314 (N29, L=056) and 1319 (N12,
L=052).

No proton events are expected at geosynchronous orbit during the
forecast period.

The greater than 2 MeV electron flux at geosynchronous orbit is
expected to be at normal to moderate levels during 26 - 29 October,
with an increase to moderate to high levels during 30 October - 01
November. Mostly normal levels are expected during 02 - 21 November.

Quiet to active levels are forecast for 26 October as effects from
the 22 October CME arrival subside. The field is expected to return
to mostly quiet levels by 27 October. Quiet to unsettled levels are
expected during 28 - 29 October as a coronal hole high-speed stream
(CH HSS) disturbs the field. A return to mostly quiet levels is
expected during 31 October - 02 November. From 03 - 05 November,
quiet to unsettled levels are expected as another recurrent CH HSS
affects the field. Mostly quiet levels are expected during 06 - 21
November.