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 143 from 2003 Sep 22 SOLAR ACTIVITY -------------- During the most of the week the activity of the Sun was dominated by a large NOAA AR 0464 (Catania number 41), which had a beta-gamma magnetic configuration. However, the background X-ray flux was approximately at the B3 level, so most of the flares produced almost every day by this active region were just of the C1 - C2 level. The strongest flares were C5.4 on September 24 and C6.8 on September 28. A low-latitude coronal hole in the southern hemisphere was in a geoeffective position close to the central meridian on September 22. A large filament in the southern hemisphere erupted around 06:00 UT - 07:00 UT on September 24. The eruption was not directed towards the Earth. GEOMAGNETIC ACTIVITY -------------------- The geomagnetic situation at the beginning of the week was very slightly disturbed (on September 22 - 23 maximal value of the Kp index was 4) because of the turbulent slow solar wind flow and the interface between two fast flows (on September 23) emanating from the ramifications of the low-latitude coronal hole in the southern hemisphere. On September 24 Kp index reached 5 as the Earth entered the interaction region between slow and fast solar wind flows. Fast flow itself (coming from the main part of the low-latitude coronal hole in the southern hemisphere) arrived in the morning of September 25 producing minor storm conditions (Kp = 5). Geomagnetic conditions at the end of the week (September 27 - 28) were quiet. --------------------------------------------------------------------------- DAILY INDICES DATE RC 10CM Ak BKG M X 2003 Sep 22 095 123 018 B2.6 0 0 2003 Sep 23 148 125 018 B3.0 0 0 2003 Sep 24 139 134 037 B3.9 0 0 2003 Sep 25 172 133 027 B2.9 0 0 2003 Sep 26 166 131 016 B3.4 0 0 2003 Sep 27 171 130 007 B3.1 0 0 2003 Sep 28 /// 137 007 B4.0 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