: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 --- Outgoing mail is certified Virus Free Thanks To Grisoft AVG. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.509 / Virus Database: 306 - Release Date: 8/12/2003 ---[Start Commercial]--------------------- World Radio TV Handbook 2003 is out! Order it now! http://www.amazon.com/exec/obidos/ASIN/0823059677/hardcoredxcom ---[End Commercial]----------------------- ________________________________________ Hard-Core-DX mailing list [EMAIL PROTECTED] http://dallas.hard-core-dx.com/mailman/listinfo/hard-core-dx http://www.hard-core-dx.com/ _______________________________________________ THE INFORMATION IN THIS ARTICLE IS FREE. It may be copied, distributed and/or modified under the conditions set down in the Design Science License published by Michael Stutz at http://dsl.org/copyleft/dsl.txt
