Subject: SOHO/LASCO HALO CME 120321 BACKSIDED

UCMEO 93001 20321 1730/
20321 60736 81242 3062/ 305// 323// 41232
20321 60646 80756 ///// 11429 1112/
99999

PLAIN

SOHO/LASCO observed a full asymmetric HALO CME on March 21, 2012.  Event is
first seen in C2 at 07:36 UT with a loop on the NE. The event expands to
a full halo by 08:12 UT.  The event continues into the C3 field beginning
07:54 to 12:42 UT leaving the C3 field at 30 Rsun in the northwest.

Time/height measurements were marked to 4 points in C2 with speeds
of 1383.5 Km/sec at position angle 306 degrees. The event is marked to 9 points
in C3. Speeds average through both fields to 1232.3 Km/sec at PA 306 degrees.
Acceleration -40.48 m/sec^2.

SDO/AIA 193/304 in eclipse 06:18-07:30 UT.  n/a

STEREO: Beacon data
COR2 A, 05:39-0754 UT data gap. First seen at 07:54 UT with LE to 5.2 Rsun. 
Event expands to an asymmetric halo (west).
Preliminary time/height measure gives 1498.7 km/sec velocity at LE. 
EUVI A, 06:05-07:15 UT data gap.  In progress 07:15-08:05 UT flare of AR 11429(?)
near the limb in NW quadrant in euvi images.  A wave and dimming are produced over
the west hemisphere.
COR2 B, At 07:40 UT a loop expands to an asymmetric (east) halo event.
Preliminary time/height measure gives 1642.4 km/sec velocity at LE.
EUVI B, 06:46-07:56 UT, AR on east limb erupts with wave over NE quadrant.

   
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/2012/120321/

Best regards,

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

BT