:Product: Weekly Highlights and Forecasts
:Issued: 2003 Oct 21 2212 UTC
# Prepared by the US Dept. of Commerce, NOAA, Space Environment Center
# Product description and SEC contact on the Web
# http://www.sec.noaa.gov/weekly.html
#
#                Weekly Highlights and Forecasts
#
Highlights of Solar and Geomagnetic Activity
13 - 19 October 2003

Solar activity ranged from very low to high levels.  An almost
spotless visible disk resulted in very low levels from 13 – 17
October.  There were a few spot groups visible during this period,
but all were small with alpha or simple beta magnetic
configurations.  Solar imagery on the 17th hinted strongly that one
or more considerably complex regions were rotating around the east
limb.  Occasional long-duration B-class activity on the 17th also
lent credence to the probability that activity levels would soon
increase.  The first of these active regions rotated into view on 18
October and was numbered as Region 484 (N05, L=351, class/area
Dac/240 on 19 October).  Activity increased to low levels on the
18th as this compact, rapidly developing region produced several low
C-class flares.  A halo CME was also observed on the 18th,
originating from behind the southeast limb.  Activity increased to
high levels on 19 October.  Region 484 produced an X1/1n flare at
19/1650 UTC.  The flare was accompanied by strong radio bursts, a
Type II radio sweep, and a coronal mass ejection.  Two M1 flares
also occurred in this region at 19/0626 UTC and 19/1926 UTC.  Region
484 grew dramatically during this 24-hour period and developed a
strong delta configuration in a spot group containing over 1000
millionths of white light areal coverage.  (Note: At the time of
this writing, Region 484 was still in growth phase, exceeding 1600
millionths in size.  Activity on the SE limb suggests that another
considerably active region is about to rotate into view.)

Solar wind data were available from the NASA Advanced Composition
Explorer (ACE) spacecraft for most of the summary period.  The
period began with the solar wind speed on a steady rise as a large
east-west coronal hole rotated into a geoeffective position.  This
recurrent coronal hole rotated into geoeffective position late on
the 13th, and the associated high speed stream peaked at near 800
km/s early on the 15th.  IMF Bz was mostly southward, as much as –15
nT early in the period.  The high speed stream was in decline but
remained elevated, generally in the 500 – 600 km/s range through the
end of the period.

There were no greater than 10 MeV proton events at geosynchronous
orbit during the period.

The greater than 2 MeV electron flux at geosynchronous orbit was at
high levels on 15 - 19 October.

Geomagnetic activity ranged from quiet to severe storm levels.  The
period began at mostly quiet to unsettled levels with isolated
active periods.  A recurrent high speed coronal hole stream became
geoeffective late on the 13th.  The geomagnetic field response was
unsettled to major storming at all latitudes with occasional severe
storm levels at higher latitudes, on the 14th and 15th, tapering off
to very isolated major storm levels by the 16th and 17th.  Elevated
solar wind speeds and periods of sustained southward Bz prolonged
the disturbance through the end of the period:  Unsettled to minor
storm levels were observed on the 18th, and again on the 19th, with
occasional major storm periods at higher latitudes on the 19th.

Forecast of Solar and Geomagnetic Activity
22 October - 17 November 2003

Solar activity is expected to range from low to high levels. 
Moderate to high levels are expected for the first half of the
period due to active regions in the eastern solar hemisphere. 
Region 484 is a very large and complex active region, capable of
producing M and X-class activity.  Activity on the SE limb late in
the period suggests another considerably active region will rotate
into view early in the forecast period and further enhance the
probability for a major flare.  Solar activity levels should
decrease for the latter half of the period as these active regions
rotate around the west limb.

There is a possibility for a greater than 10 MeV proton events at
geosynchronous orbit during the first half of the period.

The greater than 2 MeV electron flux at geosynchronous orbit is
expected to reach high levels on 22 – 26 October, 3 – 4 November,
and again on 10 - 17 November.

The geomagnetic field is expected to range from quiet to major storm
levels during the period.  A coronal hole currently in a
geoeffective position will produce unsettled to minor storm levels
on the 22nd and 23rd. There is a chance for some transient effects
on the 23rd and 24th due to recent CME activity on the eastern
hemisphere, but most CME material did not appear to have an
earthward component.  Geomagnetic activity for the remainder of
October through early November is expected to be mostly quiet to
unsettled with isolated active periods (barring any CME impact). 
Isolated minor to major storm periods are possible on 09 – 17
November due to a high speed coronal hole stream.