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 176 from 2004 May 10 SOLAR ACTIVITY: --------------- The week started very quiet: a B4.4 flare on May 10, only a B1.0 flare was reported. A partial halo CME was seen. The CME was probably associated with a B1.9 flare peaking at 03:55UT coming from NOAA active region 0604. The CME never did reach the earth: it was slower than the solar wind speed at that moment. From May 12 on, sunspot group 26 (NOAA 0609) entered on the scene releasing a C1.3 flare. Until May 16, this group was the only flaring source. It produced two other C-flares on May 13. The growth of this group is worth mentioning: in a MDI movie with pictures taken in visible light, the group consisted of only a few small dots on May 12, on May 14 it was already visible with the naked eye! May 15, the group split in two. On May 16, sunspot group 31 (NOAA 0614) suddenly popped up on the west-side of the solar disk producing a B4.5. Today, May 17 it produced already two C-flares. The solar wind speed stayed at a plateau slightly above 400 km/s from May 10 until May 14. Beginning of May 15 is started to decrease until 300 km/s. There was no signature in the solar wind speed of a coronal hole. GEOMAGNETISM: ------------- It was quiet the whole week except for a small time interval on May 12, 13 and 15 when the K_p index estimated by NOAA reached 4. At that moment, the B_z component of the IMF reached a value between -5nT and -10nT. --------------------------------------------------------------------------- DAILY INDICES DATE RC 10CM Ak BKG M X 2004 May 10 056 93 /// A7.3 0 0 2004 May 11 041 90 /// A6.0 0 0 2004 May 12 064 99 /// A7.6 0 0 2004 May 13 079 101 /// B1.4 0 0 2004 May 14 098 110 /// B1.6 0 0 2004 May 15 103 115 /// B2.1 0 0 2004 May 16 126 118 /// B1.9 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