Subject: SOHO/LASCO HALO CME 130421 BACKSIDED

UCMEO 93001 30422 1800/
30421 60736 81406 2812/ 280// 323// 40883
30421 60645 80745 ///// 11719 1112/
99999

PLAIN

SOHO/LASCO observed a HALO CME on April 21, 2013.  Event is first seen in
C2 at 07:36 UT as a bright loop with cavity and core. The front expands with
extensions to a full HALO CME by 08:36 UT. The event continues into the C3
field beginning 08:06 to 14:06 UT leaving the C3 field of view at 30Rsun in
the West hemisphere. 

Time/height measurements were marked to 4 points in C2 with speeds of 928.7 Km/sec
at position angle 281 degrees. The event is marked to 9 points in C3.  Speeds average
through both fields to 882.8 Km/sec at PA 281 degrees.  Acceleration -14.07 m/sec^s.


SDO/AIA 193A shows a far-side CME over the West limb 06:36-08:00 UT. A wave is
seen expanding along the west limb with minimal material on disk.

STEREO: BEACON Data
COR2 A, 07:54-11:54 UT, full HALO CME expanding with bright loop over the East 
hemisphere.
Preliminary time/height measure gives 717.0 km/sec velocity at LE. 
EUVI A, 06:45-07:45 UT, flare of AR11719 on disk near central meridian at
location [N10, W133]. The event produces a dimming and wave with bright arcade.
COR2 B, 07:39-10:39 UT. Expanding partial HALO CME over the East hemisphere.
Preliminary time/height measure gives 843.0 km/sec velocity at LE.  
EUVI B,  n/a

   
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/2013/130421/

Best regards,

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

BT