:Issued: 2011 Jan 17 1726 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 524 from 2011 Jan 10
SOLAR ACTIVITY
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Four sunspot groups were reported by Catania during the week: 91, 96, 97 and 98 (NOAA ARs 1140, 1145, 1146, and 1147, respectively). The first three groups did not generate flaring activity above the B5 level.
On January 14-16 the flaring activity was dominated by the Catania sunspot group 98 (NOAA AR 1147). On January 14, while still behind the north-east solar limb (returning NOAA AR 1138), it produced C1.6 and C1.0 flares peaking at 03:30 and 13:07 UT respectively. After its appearance from behind the east solar limb, Catania sunspot group 98 produced a C1.1 flare peaking at 14:19 UT on January 15. On January 16 the flaring activity of Catania sunspot group 98 decreased to the B-level.
A low-latitude coronal hole in the northern hemisphere reached the solar central meridian on January 10. A fast solar wind flow from this coronal hole arrived at the Earth on January 13 (see below). Another low-latitude coronal hole, this time in the southern hemisphere, reached the solar central meridian on January 14.
GEOMAGNETIC ACTIVITY
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In the beginning of the week, the Earth was situated inside the trailing part of a fast solar wind stream. The interplanetary magnetic field (IMF) magnitude was at the average level, so the geomagnetic conditions were quiet. Late on January 13, the fast solar wind flow from a low-latitude coronal hole in the northern hemisphere (see above) arrived at the Earth. The IMF magnitude did not reach particularly high values either in the stream interaction region or in the fast flow itself, so the geomagnetic situation remained quiet. On January 16 the solar wind speed decreased and an interplanetary sector boundary was crossed in the end of the day, possibly giving an early warning of the approaching fast solar wind stream from a low-latitude coronal hole in the southern hemisphere. As the IMF magnitude remained at the average level, the geomagnetic conditions stayed quiet.
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DAILY INDICES
DATE RC EISN 10CM Ak BKG M X
2011 Jan 10 035 019 83 008 A7.2 0 0
2011 Jan 11 024 016 83 012 A6.5 0 0
2011 Jan 12 026 015 80 007 A6.8 0 0
2011 Jan 13 013 007 80 012 A7.3 0 0
2011 Jan 14 000 000 79 016 A9.3 0 0
2011 Jan 15 011 000 80 004 B1.0 0 0
2011 Jan 16 /// 009 80 006 A7.3 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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