Date: Sat, 4 Sep 2004 17:13
From: Guillermo Stenborg
Subject: 'Full' Halo CME on 2004/09/04, backsided
UCMEO 93001 40904 2110/
40904 60654 81718 0002/ 360// 123// 20970
///// ///// ///// ///// ///// /////
99999
PLAIN
BT
LASCO/EIT observed an asymmetric 'full' halo CME on 2004/09/04.
The event was first observed in C2 at 06:54 UT above the E Limb
as a bright loop front. By 07:31 UT a wide and bright loop front
can be seen developing mainly toward E accompanied by a much
fainter and diffuse loop front extending all above the N Pole.
By 08:06 UT the C2 occultor is completely covered (with very
faint extensions above the SW Limb). Please note that by 08:30 UT,
above the NE Limb, an apparently flat ragged front is discernible
superposed in the LOS with our event.
On the other hand, features corresponding to the halo event are
first seen in C3 at 07:42 UT above the E - ESE Limb, exhibiting
a diffuse front ahead of a bright loop front. The C3 occultor is
covered by 08:42 UT. For reference, the mean plane-of-sky speed
for the LE of various features is given below (based on C3 data):
- LE of the diffuse front at PA 112: 970 km/sec
- LE of the bright loop front at PA 112: 850 km/sec
- LE of the outermost feature at PA 295: 457 km/sec
GOES did not record any significant X-ray activity by the time.
EIT Fe XII images show a CME signature that develops above the
E Limb, starting at around 07:36 UT. Such an ejection seems to
be rooted with one leg on the visible side and the other one
behind the limb. It is most likely the EIT counterpart of the
'flat' front mentioned above. As for the halo event, there is
no visible signature on the Earthside of the Sun as seen on EIT
Fe XII images that could be associated. The event has therefore
been determined as an asymmetric 'full' halo CME, backsided.
Movies of the event will shortly be made available at:
ftp://ares.nrl.navy.mil/pub/lasco/halo/20040904
Due to unforeseen factors the 'gif' images will be made available
on Tuesday. I'm sorry for that.
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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