Solar Influences Data Center (SIDC) / RWC Belgium
Royal Observatory of Belgium
E-mail: Pierre.Cugnon@oma.be
http://sidc.oma.be

SIDC WEEKLY BULLETIN
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WEEK 157 from 2003 Dec 29  

SOLAR ACTIVITY:
---------------
The solar activity was low during the whole period. Only one M flare was
produced on 31/12/03 by active region Catania#20 (NOAA0528), while this 
active region was passing behind the West limb. After 31/12/03, the 
dominant active region was Catania#30 (NOAA0536), which  consisted of a 
very large sunspot. However, until Jan. 4,this region did not develope 
a complex magnetic structure and only produced a few C flares. However, 
late on Jan. 4, it started to become more active, and other stronger 
flares (M or X flares) can be expected in the current week.

GEOMAGNETIC ACTIVITY:
---------------------
The week started with quiet to unsettled conditions, as the influence of 
a high-speed solar wind stream decayed on the first day of the period. 
On 31/12/03 around 11:00UT, the Earth entered a new high-speed stream 
which disturbed the geomagnetic field for the rest of the week. The 
solar wind speed rose to 600km/s, and the N-S component of the 
interplanetary magnetic field oscillated between +5 and -10nT, except 
for a temporary decrease to 450km/s on 2/1/04. Minor storms (Kp=5) 
occured on 31/12/03 12:00-20:00UT, on 1/1/04 05:00-14:00UT, on 
3/1/04 08:00-12:00UT and late on 4/1/04. These disturbed geomagnetic 
conditions are expected to continue for at least 4-5 days, under
the influence of a coronal hole now located in a geoeffective position.

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DAILY INDICES
DATE           RC   10CM   Ak   BKG    M   X
2003 Dec 29   ///   115   006   B2.7   0   0
2003 Dec 30   043   108   009   B2.8   0   0
2003 Dec 31   025   106   028   B3.9   1   0
2004 Jan 01   059   116   026   B7.5   0   0
2004 Jan 02   072   117   018   B3.0   0   0
2004 Jan 03   083   116   025   B2.6   0   0
2004 Jan 04   095   119   023   B3.2   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)
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NOTICEABLE EVENTS
DAY BEGIN MAX  END  LOC   XRAY OP  10CM   TYPE               Cat  NOAA NOTE
31  1821 1824 1826 N10W89 M1.0          III/3                 20  0528 SXI derived location