Date: Tue, 20 Jul 2004 08:53
From: Guillermo Stenborg
Subject: 'Partial' Halo CME on 2004/07/19, most likely frontsided
UCMEO 93001 40720 1300/
40719 61330 80318 3201/ 200// 223// 20270
40719 61047 81055 14207 10652 1112/
99999
PLAIN
BT
LASCO & EIT observed a most likely partly Earth-directed
event on 2004/07/19, which showed up in the LASCO coronagraphs
FOV as a 'partial' Halo CME. The event was first clearly
discerned in C2 at 13:30 UT spanning from ~ PA 320 - 170,
just after a short data gap (12:06 - 13:30 UT). A bright
loop-like feature is also seen above the ENE Limb, which
develops exhibiting an apparently twisted trailing part.
The event is first seen in the C3 FOV at 13:42 UT above the
ENE Limb. By 19:42 UT spans ~ 240 deg fro PA 320 - 200.
The mean plane-of-sky speed of the event as measured
at the leading edge (LE) of the outermost front at PA ~070, was
~270 km/sec (based on C3 data), showing a slight acceleration.
On the other hand, the mean plane-of-sky speed of the LE of
the bright loop on ENE was ~192 km/sec at the same PA (based
on C2 and C3 data), showing also a slight acceleration.
The event was associated with complex solar activity reported
by GOES on the visible side of the solar disk, more precisely,
related to activity above the NOAA AR 0652, and to a lesser
extent NOAA AR 0653. The former AR produced several C-class
X-ray flares during the day. In particular, the C2.9 X-ray flare
reported to occur between 10:47 - 10:55 UT with peak emission at
10:52 UT on AR 0652 (N07E42) was most likely associated to the
halo event. It is also worth to mention the C2.5 X-ray flare
occurred on NOAA AR 0653 (S12E52) between 13:00 - 13:22 UT with
peak emission at 13:14 UT. On the other hand, EIT Fe XII running
difference images show a brightening above AR 0652 at 10:48 UT
with a dimming developing mainly NW afterward.
The complex event has therefore been determined as, at least,
a 'partial' halo CME, most likely frontsided.
Images and movies of the event will shortly be made available at
ftp://ares.nrl.navy.mil/pub/lasco/halo/20040719
Best wishes,
Guillermo Stenborg
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Dr. Guillermo A. Stenborg
SOHO-LASCO Operations Scientist,
CUA, MC 682.3, Bldg 26, Rm 001, F: +1-301-286-0264
NASA Goddard Space Flight Center,
Greenbelt, MD 20771. P: +1-301-286-2941
e-mail: stenborg@kreutz.nascom.nasa.gov
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