:Product: Weekly Highlights and Forecasts
:Issued: 2003 Sep 23 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
15 - 21 September 2003

Solar activity ranged from low to moderate levels.  The period began
on 15 September with low level activity.  Region 456 (S07, L=221,
class/area Dai/240 on 13 September) produced an M1 flare at 2244 UTC
on 16 September from just beyond the west limb.  Activity for the
remainder of the period (17 – 21 September) was at low levels. 
Region 461 (N13, L=159, class/area Dao/250 on 18 September)
developed on 16 September and grew quickly in the over the next
three days.  This region produced some minor C-class flares before
it rotated beyond the west limb on 20 September.  Region 464 (N03,
L=353, class/area Eko/460 on 21 September) rotated onto the visible
disk on 20 September and activity from this region consisted of
minor C-class flares.

Solar wind data were available from the NASA Advanced Composition
Explorer (ACE) spacecraft for most of the summary period.  Early on
16 September a slow transient was observed passing the ACE
spacecraft.  Total IMF measurements (Bt) reached 12 nT and Bz values
were –5 to –10 nT.  By late on 16 September, a large coronal hole
high speed stream rotated into a geoeffective position with solar
wind speeds increasing from 450 to over 800 km/s by 17 September. 
The Bz component of the IMF reached –10 to –15nT at the onset of the
coronal hole and from 18 – 21 September Bz was oscillating between
+/- 7nT.  Solar wind speed was near 800 km/s on 18 September before
beginning a slow decline.  By the close of the period solar wind
speed was down to 550 km/s.

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 reached
high levels on 15 September and again on 17 – 21 September.

Geomagnetic activity ranged from quiet to severe storm levels.  The
period began with quiet to unsettled conditions on 15 September. 
The slow transient observed on 16 September produced active to major
storm levels.  The coronal hole high speed stream produced severe
storm levels on 17 September and major storm levels on 18 September.
Active to minor storm levels were observed from 19 – 21 September
during the decline phase of the high speed stream.

Forecast of Solar and Geomagnetic Activity
24 September - 20 October 2003

Solar activity is expected to range from very low to low levels with
a chance of isolated M-class events.  Region 464 has the potential
for isolated M-class activity early in the period before it rotates
beyond the west limb on 02 October.  From 02 October until Region
464 returns on 15 October, activity is expected to be at low levels.

No greater than 10 MeV proton events at geosynchronous orbit are
expected during the period.

The greater than 2 MeV electron flux at geosynchronous orbit is
expected to reach high levels on 19 – 23 September, 02 – 05 October,
07 – 09 October, and 16 – 20 October.

The geomagnetic field is expected to range from quiet to major storm
levels during the period.  Residual effects from the coronal hole
high speed stream are possible early in the period with possible
isolated minor storm levels.  Another coronal hole is due to return
on 01 – 03 October and is expected to produce mostly active
conditions with possible isolated minor storm levels.  A returning
coronal hole on 05 – 08 October is expected to produce active to
isolated minor storm levels.  The large coronal hole that just
departed the disk is due to return on 14 – 20 October and is
expected to produce major storm levels.