[HCDX] SIDC Belgium Past Week Summary Of Solar & Geomagnetic Activity

["Thomas Giella KN4LF" <kn4lf@xxxxxxxxxxxxxxx>]

:Issued: 2003 Aug 18 1526 UTC
:Product: documentation at http://sidc.oma.be/products/bul
 SIDC Weekly bulletin on Solar and Geomagnetic activity                       
WEEK 137 from 2003 Aug 11  

SOLAR ACTIVITY

Solar activity was low during the past week. The biggest sunspot group
of the previous week, Catania 90 (NOAA 0424) was still the dominant source
of solar activity at the beginning of the week, although it was already
in its decay phase and approaching the western limb. In the mean time,
Catania sunspot group 96 (NOAA 0431), which had appeared at the eastern
solar limb on Aug 9, was developing rapidly, and soon took over the torch
from sunspot group 90. It remained the most active group for the rest of
the week, producing a multitude of C-flares. Still, despite the fact that
this group developed a complex magnetic configuration (beta-gamma-delta)
and grew to considerable size (more than 70 spots covering slightly more
than 0.07% of the solar disk), no M-flares occurred. The largest flare
observed was a C7.7 on Aug 14. Shortly after, on Aug 15, the group reached
its peak, and started to decay.

On Aug 14, a short time after 20:00UT, a full halo CME was observed by
LASCO. Although at first this event was thought to be backsided, we now
believe that the CME originated in group 96, where EIT images clearly
show enhanced activity about half an hour earlier.  

GEOMAGNETIC ACTIVITY

Geomagnetic activity was quiet at the start of the week, but from about
midday (UT) on Aug 11, the influence of a small coronal hole became visible,
pushing up the solar wind speed to approximately 700km/s on Aug 12. The
interplanetary magnetic field remained mostly northwards however, limiting
the geo-effectiveness of this high speed wind stream. This resulted in
active geomagnetic conditions during the second half of Aug 11 and on Aug 12
(the K-index in Wingst was mostly at 4 during this time). From Aug 13
onwards, the solar wind speed slowly decreased to 550km/s, was briefly
pushed back up to 600 km/s on Aug 15, but then rapidly decreased to about
400km/s at midday UT on Aug 17. On the same day, the earth\\\'s geomagnetic
field was perturbed by a shock in the solar wind. The shock was recorded
by both ACE and SOHO/CELIAS at approximately 13:40 UT. Although the increase
of the solar wind speed was moderate, jumping up by about 100km/s to a
little above 500km/s, this shock led first to minor geomagnetic storm
conditions, followed later by a major geomagnetic storm when the
interplanetary geomagnetic field turned strongly southwards (at 01:00 UT
on Aug 18). This storm is still ongoing. 

DAILY INDICES
DATE           RC   10CM   Ak   BKG    M   X
2003 Aug 11   099   129   014   B3.2   0   0
2003 Aug 12   120   123   026   B2.7   0   0
2003 Aug 13   132   131   017   B6.0   0   0
2003 Aug 14   099   130   017   C1.0   0   0
2003 Aug 15   134   131   016   B6.8   0   0
2003 Aug 16   122   127   012   B4.0   0   0
2003 Aug 17   151   119   021   B3.7   0   0

# RC  : Sunspot index from Catania Observatory (Italy)
# 10cm: 10.7 cm  radioflux (DRAO, Canada)
# Ak  : Ak Index Wingst (Germany)
# BKG : Background GOES X-ray level (NOAA, USA)
# M,X : Number of X-ray flares in M and X class, see below (NOAA, USA)

NOTICEABLE EVENTS
DAY BEGIN MAX  END  LOC   XRAY OP  10CM   TYPE               Cat  NOAA NOTE
NONE


73,
Thomas F. Giella
Space & Atmospheric Weather Forecaster
C/S KN4LF
4208 Thackery Way
Plant City, FL, USA 33566
EL87WX

SWFWMD Rainfall Observer #574
NWS Tampa Bay, FL Skywarn Spotter #HIL-249 

Florida Space & Atmospheric Weather Institute:
http://www.kn4lf.com/fsawi.htm
 




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