Halo CME Mail

Date: Wed, 16 Aug 2006 14:41

From: Guillermo Stenborg

Subject: a) Faint asymmetric Halo Event on 2006/08/16, most probably , frontsided


Status: O

UCMEO 93001 60816 1840/
60816 60731 81642 0001/ 360// 113// 10600
60816 60454 80819 31613 10904 1212/
99999
 
PLAIN


LASCO/EIT observed a couple of Halo events on 2008/08/16. The first one 
was a very faint asymmetric Halo Event first seen in the C2 FOV at 07:31
UT, while the second one was a very intense asymmetric Halo first seen
at 16:30 UT. In this Alert the first event will be reported. And as soon as 
more LASCO images become available, the Alert for the second (and most 
important) event will be issued.

Therefore, the first event was first seen in C2 at 07:31 UT appearing
above the W Limb as a ragged and diffuse front preceding the development 
toward SW of a system of wide and expanding (brighter) loop fronts. The 
outermost front seems to fully cover the C2 occulting disk by 09:08 UT. 
The signal on the eastern hemisphere is extremely faint and just above 
the occulting disk, while on W it is already past the outer edge of the 
C2 FOV. The event is first seen in C3 at 08:18 UT appearing above the SW 
limb as a diffuse loop front. The brighter system of loops shows up at 
10:19 UT. By that time, the outer front fully surround the C3 occulting 
disk (signal on the eastern hemisphere just above the occulter). The mean
plane-of-sky speed of the outermost front of the event (very faint and 
diffuse) at PA 230 was ~ 600 km/sec (based on C3 data), showing
practically no acceleration.

GOES reported prior and during the time of the LASCO event, a couple of 
impulsive B-class X-ray flares on NOAA AR 10904 on top of B-level X-ray 
activity: 

i) a B2.1 (at S11W09) between 04:54 - 05:00 UT with peak at 04:57 UT, and 
ii) a B3.4 (at S13W16) between 08:12 - 08:19 UT with peak at 08:15 UT.

EIT 195 images show the formation of a dimming region to N of AR 10904 
starting at 07:13 UT. Between 08:48 - 11:46 UT, formation of loops
connecting from quiet Sun and AR 10904 to bright plasma NW of AR. At 
10:14 UT, loops in center of AR open and appear to eject material.

In summary, the event has therefore been determined as a very faint
asymmetric full Halo Event, probably frontsided, based on the spatial 
and temporal correlation with the activity observed on and around AR 10904.

LASCO/EIT movies and images of the event will shortly be made available
at:

ftp://ares.nrl.navy.mil/pub/lasco/halo/20060816a


Best wishes,
	Guillermo Stenborg

++
Dr. Guillermo A. Stenborg   
SOHO-LASCO Operations Scientist,                                           
CUA, MC 612.5, 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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