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 156 from 2003 Dec 22 SOLAR ACTIVITY: --------------- One sunspot goup dominated the solar activity last week: 20 (NOAA 0528). During the beginning of the week he produced a series of C-flares, with a final M1.5 flare on Dec 26. GEOMAGNETISM ------------- The transequatorial coronal hole with an elongated north-south shape which became geoeffective on 20 Dec had not much influence on the geomagnetism. The solar wind speed reached the range of 600-650 km/s on Dec 22 and started decreasing at the beginning of Dec 23. The interplanetary magmetic field remained mostly northwards, and thus geomagnetic perturbations remained limited to active conditions. Only Izmiran recorded K=5 at 15.00 UT on Dec 22. The rest of the week, geomagetic conditions were quiet. --------------------------------------------------------------------------- DAILY INDICES DATE RC 10CM Ak BKG M X 2003 Dec 22 /// 138 020 B3.8 0 0 2003 Dec 23 133 142 011 B4.6 0 0 2003 Dec 24 105 139 009 B3.8 0 0 2003 Dec 25 068 139 005 B4.5 0 0 2003 Dec 26 053 137 008 B3.5 1 0 2003 Dec 27 049 127 014 B2.8 0 0 2003 Dec 28 /// 119 014 B2.5 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 26 1913 1928 1933 N09W30 M1.5 1N 20 0528