Halo CME Mail

Date: Fri, 8 Sep 2006 16:21

From: Guillermo Stenborg

Subject: Faint asymmetric Halo in LASCO in C2 on 2006/09/08


Status: O

UCMEO 93001 60908 2020/
60908 60012 81442 0003/ 360// 113// /////
60908 60130 80245 20607 10909 1//1/
99999
 
PLAIN


LASCO C2 apparently observed a faint asymmetric Halo Event on 2006/09/08. 
LASCO data are too scarce to be sure about the event due to the fact that 
LASCO is not being recorded during DSN Telemetry Data gaps (this is 
happening since 08/28 and will last until 09/16). In particular, the DSN 
data gaps in 09/08 were (are) as follows:

    - last C2 frame before gap: 00:24 UT

* 00:30 - 04:05 UT : DSN Data gap

    - first C2 frame after gap: 04:12 UT
  
    - last C2 frame before gap: 05:24 UT
  
* 05:30 - 13:55 UT : DSN Data gap

    - first C2 frame after Data gap: 14:24 UT
  
    - last C2 frame before gap: 16:36 UT

* 17:00 - 23:15 UT : DSN Data gap

With these considerations in mind, I'll just proceed to describe the
facts. A bright loop front starts to be seen in C2 on WNW at 00:12 UT, its 
development missed in the data gap. By 04:24 UT the loop front is close to 
the outer edge of C2. It appears surrounded by a fainter and much wider
front spanning all across the western hemisphere up to past the S Pole. 
Just before the second data gap, the C2 occulter seems to be surrounded, 
though the signal on E is barely discernible and only very close to the 
occulting disk. More faint wide loop fronts continue appearing on W. 

Only one C3 frame (05:18 UT) shows something of the event. Though the 
event covers a big angle in the western hemisphere, the S Pole is not 
crossed by that time. Afterwards, there is a data gap, so nothing else 
can be said.

After this second gap, C2 shows a loop front already developing on WSW.
Very faint and diffuse loop-like extensions seems to be developing 
above the S Pole. C3 shows no remnant signatures of any Halo event.

No EIT images are available due to EIT CCD bakeout (the bakeout will last 
until 09/16). GOES recorded a couple of short duration B-class X-ray
flares on NOAA AR 10909 during the time of the first LASCO data gap: 
i) a B4.4 on S07E06 between 01:30 UT - 01:47 UT with peak emission at 
01:39 UT, and ii) a B3.3 on S07E05 between 02:34 - 02:45 UT with peak 
emission at 02:39 UT. And then during the second data gap, it recorded 
a B5.6 on the same AR (S06E01) between 10:13 - 11:46 UT with peak emission 
at 10:58 UT.

In summary, an apparently faint and asymmetric Halo Event was
observed by LASCO C2. It is hard to say whether the different structures
mentioned above belong to a unique event. It seems to exist a temporal
correlation between the activity on AR 10909 and the faint and diffuse
wide loop-like extensions aforementioned. 

LASCO C2 movies and C2/C3 images of the event will shortly be made 
available at:

ftp://ares.nrl.navy.mil/pub/lasco/halo/20060908


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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