Subject: SOHO/LASCO Partial HALO CME 120427 BACKSIDED

UCMEO 93001 20428 1330/
20427 61624 80018 1362/ 040// 333// 30757
20427 61557 81621 ///// 11463 1//2/
99999

PLAIN

SOHO/LASCO observed a partial HALO CME on April 27, 2012.  Event is first
seen in C2 at 16:24 UT with a bright loop over the equatorial west.
Approximate width of the CME spans pa 136-40 degrees totaling 264 degrees.
The event continues into the C3 field beginning 16:54 to 00:18 UT leaving
the C3 field at 30 Rsun in the Southwest.

Time/height measurements were marked to 4 points in C2 with speeds 
of 898.4 Km/sec at position angle 268 degrees. The event is marked to 17 points 
in C3. Speeds average through both fields to 756.6 Km/sec at PA 272 degrees.  
Acceleration -12.86 m/sec^2.

SDO/AIA 193 shows a cme behind limb over the Southwest 15:57-16:21 UT.

STEREO: Beacon data
COR2 B, partial halo over the east beginning 16:24 UT,
Preliminary time/height measure gives 849.0 km/sec velocity at LE.
EUVI B, No evidence seen in field.  n/a
COR2 A, 14:54-19:24 UT data gap.  First frame 19:24 UT symmetric halo cme close
to edge of field in progress.
EUVI A, 14:55-19:15 UT data gap.  n/a

   
The observation of this event is considered 'FAIR'. 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/2012/120427/

Best regards,

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

BT