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:Issued: 2005 May 24 1501 UTC
:Product: documentation at http://sidc.oma.be/products/bul
#--------------------------------------------------------------------#
# SIDC Weekly bulletin on Solar and Geomagnetic activity #
#--------------------------------------------------------------------#
WEEK 229 from 2005 May 16
SOLAR ACTIVITY
--------------
The period started very active with 3 M-flares, all coming from active
region NOAA 763 (Catania 65), which developed a beta-gamma configuration.
However, early Tuesday May 17, strong flaring stopped and did not get
above minor C-flares again for the rest of the week.
A halo CME was observed early on Mon May 16 by the LASCO C2 coronagraph.
The event was first seen in NE direction from 13h50 UT onwards. A first
CACTus analysis shows that its speed is of the order of 500 km/s. The
event was most likely related to an eruption in active region NOAA 759
around 13h00 and is thus determined to be front-sided.
LASCO/EIT observed another very faint full halo CME on 2005/05/17. The
event was first seen in C2 at 03:50 UT as an extremely faint and diffuse
brightening all around the occulting disk. A very rough estimation of the
mean plane-of-sky speed of the LE of the event based on C2 data (where at
least it is possible to measure something) is ~ 300 km/sec (at PA 211).
The event was determined as a very faint Full Halo CME, frontsided,
associated with an M-class X-ray flare on NOAA AR 10763.
On noon Saterday May 21, the SIDC issued a \\\\\\\'all quiet alert\\\\\\\'
for 48hours. Indeed no C-class flares, geomagnetic storms or proton flux
enhancements occured during this period.
There were enhanced proton flux levels in the beginning of the period (May
16 and May 17) but the threshold level was not reached. These enhanced
values corresponded to the decay phase of the event of May 14 & 15.
GEOMAGNETIC ACTIVITY
--------------------
The period started in the aftermath of very strong geomagnetic activity on
May 15. On Monday May 16, the NOAA estimated Kp still reached a value of
6, but from Tuesday May 17 onwards, the geomagnetic conditions stabilised
and did not get above K=4 for several days.
A relatively small disturbance in the solar wind was observed by ACE at
03h30 on Fri May 20. This disturbance was probably due one of to the
weak/slow halo CMEs of May 16 and May 17. While the solar wind speed made
only a small jump (from 450 to 480 km/s), there was a significant
southward turning of the interplanetary magnetic field (down to -10nT for
several hours). This caused a relatively strong deviation of the K-index
(Izmiran: 5, Dourbes: 4).
After that, the geomagnetic activity declined from K=4 on Sat May 21 till
K=2 on Saterday evening and K=1 on Monday.
---------------------------------------------------------------------------
DAILY INDICES
DATE RC 10CM Ak BKG M X
2005 May 16 066 99 032 B2.7 2 0
2005 May 17 050 90 019 B1.4 1 0
2005 May 18 036 84 010 A8.8 0 0
2005 May 19 048 85 010 A6.9 0 0
2005 May 20 022 84 024 A8.4 0 0
2005 May 21 011 82 021 A9.4 0 0
2005 May 22 037 82 011 A6.9 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 TENCM TYPE Cat
NOAA NOTE
16 0233 0243 0250 S17E17 M1.4 1B 61 V/2,III/3 65
0763
16 0856 0908 0915 S17E15 M1.6 SF 29 III/2 65
0763
17 0231 0239 0252 S16W01 M1.8 1B 100 II/2,IV/1,III/2 65
0763
#--------------------------------------------------------------------#
# Solar Influences Data analysis Center - RWC Belgium #
# Royal Observatory of Belgium #
# Fax : 32 (0) 2 373 0 224 #
# Tel.: 32 (0) 2 373 0 491 #
# #
# For more information, see http://sidc.oma.be. Please do not reply #
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