Date: Mon, 12 Apr 2004 12:57
From: Guillermo Stenborg
Subject: 'Full' Halo CME on 2004/04/11, backsided
UCMEO 93001 40412 1715/
40411 61154 81942 0002/ 360// 133// 41184
///// ///// ///// ///// ///// /////
99999
PLAIN
BT
LASCO observed a full halo CME on 2004/04/11. The event was
first observed in C2 at 11:54 UT as a very bright loop front
above the NW limb. By 13:54 UT the front has the appearance
of an asymmetric full halo CME in C2 FOV, though extremely
faint on the SE limb. The front first appeared in C3 images
at 12:18 UT as a thick and bright loop front, the bulk of
the ejecta developing mainly toward WNW. By 15:42 UT the C3
occultor is completely covered. The mean plane-of-sky speed
for this event at PA 291 was 1184 km/s (based only in C3 data)
and showing a slight deceleration. For reference, the mean
plane-of-sky speed at different PA as obtained from C3
measurements is given below:
PA 000: 683 km/s
PA 048: 421 km/s
PA 199: 584 km/s
PA 248: 909 km/s
No X-ray event is recorded by GOES by the time. EIT Fe XII
running difference images show signatures of a big CME coming
out from behind the disk (all above the west limb) starting at
11:36 UT. This event has therefore been determined as backsided.
Movies and images of the event will shortly be available at:
ftp://ares.nrl.navy.mil/pub/lasco/halo/20040411b
Best wishes,
Guillermo Stenborg
++
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
++