Solar Influences Data Center (SIDC) / RWC Belgium Royal Observatory of Belgium E-mail: Pierre.Cugnon@oma.be http://sidc.oma.be SIDC WEEKLY BULLETIN -------------------- WEEK 109 from 2003 Jan 27 SOLAR ACTIVITY -------------- Solar activity was remarkable low this week with a 10cm radio flux in the range 120-127 and a GOES X-ray background at the B2 level. NOAA active region 266 (Catania sunspot group 25) had a beta-gamma configuration in the beginning of the week but did not produce any noticeable event. Towards the end of the week, activity started to rise as NOAA active region 274 (Catania sunspot group 35) appeared. This active region produced many smaller flares, as well as the only M-flare this week. Two spectucular prominence eruption were observed with EIT, one on Monday (2003/02/27, 22:33 - 23:33 UT) centered around S22W22, and another on Thursday (2003/01/30,between 06:13 - 09:33 UT), centered around N12W02. The first one had post-eruptive loops at the C2.4 X-ray level and possibly an EIT dimming. This prominence eruption was the most likely precursor to a partial halo CME that was first observed by LASCO C2 at 22:23 UT as a bright loop front over the South pole. The second prominence eruption was followed by a full halo CME first observed by LASCO C2 at 09:39 UT as a ragged loop front over the NW limb.The mean plane-of-sky speed for this event was 567 km/s at PA 355, with evidence for moderate acceleration. Please note that as a result of the special campaign to observe comet C/2002 X5 (Kudo-Fujikawa) the event timing by LASCO and EIT has been somewhat inaccurate this week. GEOMAGNETIC ACTIVITY -------------------- The most prominent geomagnetic event (Kp = 5-6) this week was a storm that started on Saturday evening (2003/02/01, 18h00) and that was ongoing on Sunday evening. This storm was caused by the full halo CME that left the Sun on Thursday morning (2003/02/01, 9h39, see above). At the arrival of the CME at the L1 point, ACE recorded an increase of the solar wind speed from 400 to more than 800 km/s. Two other geomagnetic storms have been recorded, one from Jan 29-15h00 UT till Jan 30-21h00 UT, and the other one on January 31 (from 06h00 till 15h00 UT). The origin of these smaller events is harder to track but the first might be related to the partial halo CME described above. --------------------------------------------------------------------------- DAILY INDICES DATE RC 10CM Ak BKG M X 2003 Jan 27 147 121 012 B2.0 0 0 2003 Jan 28 154 126 016 B2.0 0 0 2003 Jan 29 163 124 021 B2.5 0 0 2003 Jan 30 110 121 020 B1.9 0 0 2003 Jan 31 109 120 /// B2.8 0 0 2003 Feb 01 069 126 /// B4.5 1 0 2003 Feb 02 072 127 /// B4.2 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) --------------------------------------------------------------------------- NOTICEABLE EVENTS DAY BEGIN MAX END LOC XRAY OP 10CM TYPE Cat NOAA NOTE 01 0848 0905 0938 S15E71 M1.2 39 0276