Halo CME Mail

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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