Subject: SOHO/LASCO HALO CME 120908ab BACKSIDED

UCMEO 93001 20910 1830/
20908 60948 81754 2442/ 243// 323// 40826
20908 60825 80955 ///// 11552 2212/
99999

PLAIN

SOHO/LASCO observed a HALO CME on September 08, 2012.  Event is first seen
in C2 at 09:48 UT with a bright loop with cavity and core over the Southwest limb.
The event expands with extensions to a full halo CME by 10:36 UT.  There appears
to be 2 possible CME events in close succession.  The first event at 09:48 UT
is asymmetric and a second event symmetric beginning at 10:24 UT.
The event continues into the C3 field beginning 10:18 to 17:54 UT leaving the C3
field at 30 Rsun in the West.

Time/height measurements were marked to 6 points in C2 with speeds 
of 810.8 Km/sec at position angle 244 degrees. The event is marked to 11 points 
in C3. Speeds average through both fields to 825.9 Km/sec at PA 244 degrees.  
Acceleration 2.96 m/sec^2.

SDO/AIA : A CME is seen coming from behind limb 08:39-10:06 UT in the SW. 

STEREO: Beacon and HR data
COR2 B, 10:24-13:39 UT loop expanding over the east.
Preliminary time/height measure gives 858.8 km/sec velocity at LE.
EUVI B, 08:31-10:36 UT loop eruption over SE limb.  Post loop arcade.
COR2 A, 10:24-14:24 UT Symmetric halo.
Preliminary time/height measure gives 888.6 km/sec velocity at LE.
EUVI A, 195A shows eruption east of and around AR at location [S29, W145]
from 08:24-09:55 UT.  This is most likely AR11552.  EUVI 304 shows flaring of
the area with substantial dimming and bright post loop arcade in eruptive
filament fashion.

The observation of this event is considered 'GOOD'. This CME is determined a BACKSIDED event.

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

http://umbra.nascom.nasa.gov/lasco/observations/halo/2012/120908ab/

Best regards,

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

BT