Date: Tue, 6 Jul 2004 13:02
From: Guillermo Stenborg
Subject: 'Full' Halo CME on 2004/07/05, complex event
UCMEO 93001 40706 1800/
40705 62306 80918 0002/ 360// 723// 10964
///// ///// ///// ///// ///// /////
99999
PLAIN
BT
LASCO observed an impressive 'full' halo CME starting late on
2004/07/05. The event was first observed in C2 at 23:06 UT
already covering the occultor, much brighter in the southern
hemisphere. However, close examination of its early evolution
in C2, would suggest that the part corresponding to the faint
front evolving above the NW limb belongs to a different event.
Hereafter, I'll refer to the HALO itself as Event # 1, and to
the accompanying faint front evolving mainly toward NW as
Event # 2, regardless their potential (or not) association.
Event # 1 is first seen in C3 at 23:18 UT above the SSW limb.
The C3 sequence of images of the complex event allows to
distinguish the signatures of Event # 2 moving ahead toward
NW. For reference, the mean plane-of-sky speed at several PA
for both events is given below (based only in C3 data):
Event # 1:
PA 008: 457 km/s
PA 090: 737 km/s
PA 141: 744 km/s
PA 206: 964 km/s
PA 260: 725 km/s
in all cases showing an slight deceleration.
Event # 2:
PA 285: 782 km/s
also showing slight deceleration (though a little bit bigger
than for previous case).
GOES records no significant X-ray activity, except for a
couple of B class flares: i) a B1.2 X-ray flare between 18:56
and 19:04 UT with peak emission at 19:00 UT on NOAA AR 0639
(N07W35), and ii) a B1.3 X-ray flare between 20:47 - 20:59 UT
with peak emission at 20:54 UT on NOAA AR 0639 (N07W36).
EIT Fe XII running difference images show signatures of an
apparently backsided CME developing toward SW between 23:12
and 23:36 UT (Event # 1?). On the other hand, an extremely
faint intensity disturbance is guessed traveling toward NW
apparently originated nearby NOAA ARs 0639 and 0640, starting
at around 21:12 UT (Event #2?).
In brief, Event # 2 (the 'Halo') has apparently no association
with the events on the visible side of the disk mentioned above
and therefore, could be catalogued as a 'full' HALO CME, most
probably backsided.
Movies and images of the complex event will shortly be
available at:
ftp://ares.nrl.navy.mil/pub/lasco/halo/20040705
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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