Halo CME MailHalo CME Mail
Date: Tue, 20 Jan 2004 15:27
From: Guillermo Stenborg 
Subject: 'Full' Halo CME on 2004/01/20, frontsided




UCMEO 93001 40120 2030/
40120 60006 80942 0001/ 360// 323// 30874
40120 61948 80136 30516 10540 1122/
99999
 
PLAIN
 
BT 

LASCO and EIT observed a 'full' halo CME on 2004/01/20. A  
bright loop front was first seen in C2 at 00:06 UT at the 
S Pole; by 00:54 UT (C2) this bright front developed in a 
'full' halo CME, the loop spanning ~120 deg from PA 130 - 250, 
with faint extensions arounding the rest of the C2 occultor. 
The front first appeared in C3 images at 00:42 UT as a bright 
rim in the S and was a 'full' halo at 01:42 UT. The mean 
plane-of-sky speed measured at several PA on C3 data resulted 
as follows:

673 km/s at PA ~054
653 km/s at PA ~095
819 km/s at PA ~135
783 km/s at PA ~180 
708 km/s at PA ~200
874 km/s at PA ~263
346 km/s at PA ~351

The measurement at PA ~180 showed the biggest acceleration.
Though the measurement at PA ~263 exhibited the faintest LE,
it is the one taken for the UCMEO code (the fastest one).

The CME was likely associated with complex solar activity 
on the visible side of the solar disk. A C8.2 X-ray flare
occurred on NOAA AR 10540 located S16W05, which GOES records 
between 19:54 and 20:08 UT with peak emission at 20:02 UT on
2004/01/19, well observed by EIT/Fe XII. At around 22:12 UT on
the same day material seems to come out from above the AR, and 
post-event loops start to develop short after that, slightly W 
of the flare site (at 00:36 UT the developing of the post-event 
loops can be well seen in EIT Fe XII data). Couple of hours 
later, features to the N and NW appear to be perturbated by what 
it  seems to be a passing wave. This event has therefore been 
determined frontsided.

Images and movies will shortly be made available at  

ftp://ares.nrl.navy.mil/pub/lasco/halo/20040120

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
++