Date: Thu, 16 Dec 2004 10:55
From: Guillermo Stenborg
Subject: 'Full' Halo Event on 2004/12/15, most probably backsided
UCMEO 93001 41216 1545/
41215 61736 80318 0002/ 360// 123// 20524
///// ///// ///// ///// ///// /////
99999
PLAIN
BT
LASCO observed a Full Halo Event, much brighter to N, on 2004/12/15.
The event was first seen in C2 at 17:36 UT above the NW limb as well
as on the N Pole. Extremely faint extensions above the S Pole and SW
Limb can also be seen, giving to the event the appearance of a Full
Halo. The development of the event shows a ragged loop-like structure
moving out toward NW (1), a little behind a much wider (and fainter)
ragged structure (2) that extends all above the W Limb, N Pole, and
up to the SE Limb. The whole event was first seen in C3 at 18:42 UT
all above the N Pole. Extensions to S are barely discernible.
The mean plane-of-sky speed (based on C3 data) of the structure
moving toward NW (1) measured at PA 311 was about 483 km/sec,
showing practically no acceleration. As for the wide ragged structure
(2), the speed at a couple of PA is given below (the HT profiles also
show practically no acceleration):
PA 315: 524 km/sec
PA 000: 516 km/sec
No significant X-ray activity was reported by GOES by the time.
There were no EIT images as EIT is performing a CCD bakeout
(2004/12/11 18:47 UT - 2004/12/28 10:00 UT).
In summary, and taking into account the very faint extensions to S,
the event has therefore been determined as a 'full' halo event, most
probably backsided.
Movies and images (only C2 and C3) of the event will shortly be made
available at:
ftp://ares.nrl.navy.mil/pub/lasco/halo/20041215
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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