Subject: SOHO/LASCO HALO CME 111004a BACKSIDED

UCMEO 93001 11004 1930/
11004 61236 91542 0312/ 030// 333// 41652
11004 61226 81326 ///// ///// 1112/
99999

PLAIN

SOHO/LASCO observed an asymmetric HALO CME on October 04, 2011.  Event is first seen in
C2 at 12:36 UT as a bright loop over the limb at pa 31 degrees. The impulsive front
expands to a full halo by 13:48.  The event continues into the C3 field beginning 13:30
to 15:42 UT at 20.4 Rsun still in progress.

Time/height measurements were marked to 4 points in C2 with speeds of 1214.9 Km/sec
at position angle 29 degrees. The event is marked to 10 points in C3 where it
slightly accelerates.  Speeds average through both fields to 1652.1 Km/sec at
PA 26 degrees.  Acceleration 31.41 m/sec^s.


SDO/AIA 193 shows rising loops behind limb in NNE at 11:30-13:18 where an impulsive
cme lifts off with minimal wave protruding over NE limb.  AIA 304 10:57-12:45 UT 
shows a filament eruption possibly triggered by new AR 11310 at [S33, E06] adjacent
to and south of filament. A large horizontal filament elevates at lat S35 beginning 
12:15 UT and lifts off in south.  This may or may not be involved in the halo seen
in Lasco.
STEREO COR2 B: 13:25-13:55, large expanding loop in N and NE of field.
EUVI B 195 shows possibly AR 11301(?) in the NE 12:26-13:26 UT with large CME from
AR on disk with dimming and wave across north and NE and over limb.  


This is most probably the cause of the full HALO event seen in LASCO.
   
The observation of this event is considered 'GOOD'. This CME is determined a BACKSIDED event.
Material may be 

Images and movies and time/height information for this event is available on the web at:

http://umbra.nascom.nasa.gov/lasco/observations/halo/2011/111004a/

Best regards,

Kevin Schenk
Solar Heliospheric Observatory (SOHO)
EIT and LASCO Operations
NASA-Goddard Space Flight Center, USA

BT