:Issued: 2010 Dec 21 0853 UTC
:Product: documentation at http://www.sidc.be/products/bul
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# SIDC Weekly bulletin on Solar and Geomagnetic activity #
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WEEK 520 from 2010 Dec 13
SOLAR ACTIVITY
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The strongest solar event in this period was a C5.3 flare from active region NOAA 11135 on Dec 15.
Other noteworthy activity was a long duration C2.3 flare on Dec 14 from NOAA 11134.
>From Dec 15-16 onwards, the complex of NOAA active regions 11131, 11133 and 11134 in the
Northern solar hemisphere rotated behind the solar limb, resulting in a downward trend in all
solar indices (F10.7, GOES X-ray curves and the LYRA and SWAP curves).
An SIDC all quiet alert was issued from Saterday Dec 18 onwards.
GEOMAGNETIC ACTIVITY
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Geomagnetic activity was low this week and characterized by the passage of a high speed solar wind
stream. The solar wind started the period at about 400 km/s and went up over 600 km/s on Dec 14.
After that, a gradual decrease was observed down to again 400 km/s by the end of the period.
Geomagnetic activity was strongest on Dec 14 and early Dec 15 with up to 1 episode of K=4. For the
rest of the period geomagnetic activity was typically at K=2 levels.
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DAILY INDICES
DATE RC EISN 10CM Ak BKG M X
2010 Dec 13 048 026 88 010 B1.1 0 0
2010 Dec 14 033 015 90 019 B1.0 0 0
2010 Dec 15 /// 008 87 010 A9.9 0 0
2010 Dec 16 023 015 84 008 A8.9 0 0
2010 Dec 17 011 007 82 006 A6.7 0 0
2010 Dec 18 011 000 81 003 A5.1 0 0
2010 Dec 19 /// 000 81 004 A4.3 0 0
# RC : Sunspot index (Wolf Number) from Catania Observatory (Italy)
# EISN : Estimated International Sunspot Number
# 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 TENCM TYPE Cat NOAA NOTE
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# Solar Influences Data analysis Center - RWC Belgium #
# Royal Observatory of Belgium #
# Fax : 32 (0) 2 373 0 224 #
# Tel.: 32 (0) 2 373 0 491 #
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