[HCDX] SIDC Weekly Space Weather Bulletin
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[HCDX] SIDC Weekly Space Weather Bulletin
:Issued: 2003 Aug 12 1100 UTC
:Product: documentation at http://sidc.oma.be/products/bul
SIDC Weekly bulletin on Solar and Geomagnetic activity
WEEK 136 from 2003 Aug 04
SOLAR ACTIVITY
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Solar activity was rather low this week, with just a single M-flare on Aug 05 from Catania sunspot group 90 (NOAA 0424). Even C-flares were only occasionally observed, totaling about 10, with several days having no C-flares at all. Most of this smaller scale activity also originated from sunspot group 90 and its close neighbor, Catania sunspot group 88 (NOAA 0425). Sunspot group 90 was the biggest group visible, reaching a maximum size of nearly 0.08% of the disk, distributed over 2 large spots and about 20 smaller ones. It had strong magnetic fields with clear polarity mixing for nearly the whole week, so it clearly did not live up to its full flaring potential. Towards the end of the week, another large and complex sunspot group, Catania 96 (NOAA 0431) rotated
over the eastern solar limb, producing C-flare activity so far.
A northern hemisphere coronal hole rotated across the visible solar disk this week. The leading edge reached the central meridian on Aug 4. This coronal hole had two clearly separated equatorial extensions, the first of which became geo-effective on Aug 6.
Several prominence eruptions were observed during the week, but none produced an Earth-directed CME.
GEOMAGNETIC ACTIVITY
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Geomagnetic conditions were quiet on the first two days of the week, when the solar wind speed was decreasing in the aftermath of a coronal hole passage. It reached a minimum of just above 400km/s on Aug 05. Early on Aug 06, an equatorial extension of a northern hemispheric coronal hole started to influence the geomagnetic environment. The solar wind speed increased in three phases, reaching a maximum of nearly 800km/s in the morning of Aug 8, following which it started to gradually decrease (almost linearly), reaching 550km/s by the end of the week. During most of this period, the interplanetary magnetic field was mainly oriented towards the north, except for a short interval early on Aug 6 and a second one starting at about noon on Aug 7, lasting about 24 hours. During these two intervals, and especially during the latter one, minor geomagnetic storm conditions were reported. On Aug 7, the K-index in Wingst reached an isolated peak of 7, being mostly at 5 before and after.!
During the last two days of the week, the IMF was northwards and geomagnetic conditions remained quiet.
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DAILY INDICES
DATE RC 10CM Ak BKG M X
2003 Aug 04 096 123 014 B2.6 0 0
2003 Aug 05 134 131 010 B3.6 1 0
2003 Aug 06 158 129 024 B2.7 0 0
2003 Aug 07 123 137 037 B3.6 0 0
2003 Aug 08 111 133 041 B3.4 0 0
2003 Aug 09 113 130 019 B3.3 0 0
2003 Aug 10 114 131 012 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
05 1243 1249 1251 S16E33 M1.7 SN 40 II/1 90 0424
73,
Thomas F. Giella
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