Subject: SOHO/LASCO Partial HALO CME 110317 BACKSIDED

UCMEO 93001 10318 1715/
10317 61236 81842 0552/ 249// 333// 40823
10317 61225 81315 ///// 11170 1112/
99999

PLAIN

SOHO/LASCO observed a partial HALO CME on March 17, 2011.  Event is first seen in 
C2 at 12:00 UT as a narrow helmut front quickly followed by a bright, large 
impulsive loop at 12:36 UT over the southeast quadrant.  The loop expands with multiloop
cores with cavity from PA 55 - 249 degrees for a total width of 185 degrees wide.  
The event is seen in first frame of C3 at 13:30 UT, expanding over the southeast centered 
along the C3 pylon. The event is tracked out to 18:42 UT at 24.5 Rsun where the event dissipates.
 
Time/height measurements were marked to 4 points from 2.6 - 6.6 Rsun in C2 with speeds 
of 763.8 km/sec, the event accelerates in C3, marked at 14 points and calculated to
velocities averaging thru both fields to 822.6 Km/sec at position angle 127 degrees with
acceleration of 15.25 m/s^2.    

STEREO EUVI 195A Behind beacon data shows a flare and cme from AR 11165/11170 grouping in 
it's southeast quadrant near the limb beginning 12:25 - 13:15 UT.
STEREO COR2 Behind shows a large CME in it's southeast field beginning 13:10 UT.
EUVI and COR2 Ahead have data gaps during these periods.
SDO AIA 171A sees a backsided CME in the southeast beginning 11:57 UT.
There were no Earthward facing events or activity.
   
The observation of this event in LASCO is considered 'GOOD'. This CME is determined a BACKSIDE 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/2011/110317/

Best regards,

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

BT