Subject: SOHO/LASCO HALO CME 120409

UCMEO 93001 20410 1830/
20409 61224 81854 3001/ 299// 333// 40884
20409 61121 81254 48816 11451 2212/
99999

PLAIN

SOHO/LASCO observed an asymmetric HALO CME on April 9, 2012.  Event is first
seen in C2 at 12:24 UT as a bright loop on the NW which expands with extensions
to a full HALO by 13:48 UT. The event continues into the C3 field beginning
13:30 to 18:54 UT where it leaves the C3 field in the NW.

Time/height measurements were marked to 4 points in C2 with speeds
measuring 866.9 km/sec at position angle 300 degrees. 
The event is marked to 9 points in C3. Speeds average through both fields
to 884.0 Km/sec at PA 301 degrees.  Acceleration -0.64 m/sec^2.


SDO/AIA 304 shows a filament located [N16,W88] become activated ~10:06 UT.
The filament is west of and adjacent to AR11451 and erupts by 11:21 UT
resulting in a dual ribbon flare of the area with a post arcade.
AIA 193 shows a cme begin slow liftoff at 11:57 UT and a flare of AR 11451
12:12-12:54 UT.

STEREO: Beacon data
COR2 A, First seen at 12:39 UT as it expands with extensions to a
partial halo over the East. 
Preliminary time/height measure gives 993.5 km/sec velocity at LE. 
EUVI A, A cme 11:55-12:45 UT from AR11451 on disk in the NE quadrant. A 
flare is seen from the region 12:25-12:55 UT.
COR2 B, almost a symmetric halo with bright LE in the west, 12:54-16:39 UT.
Preliminary time/height measure gives 614.1 km/sec velocity at LE.
EUVI B, n/a 

NOAA reports a C3.9 Xray flare of AR 11451 12:12-13:08 UT.
   
The observation of this event is considered 'GOOD'. This CME is determined a FRONTSIDED 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/2012/120409/

Best regards,

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

BT