Subject: SOHO/LASCO HALO CME 120309ab UCMEO 93001 20309 1730/ 20309 60414 90835 2921/ 291// 333// 20863 20309 60327 80433 40317 11429 1112/ 99999 PLAIN SOHO/LASCO observed a HALO CME on March 9, 2012. Event is first seen in C2 at 04:14 UT as a symmetric halo with a second event in close succession seen by 04:38 UT. There is a substantial amount of proton emission in the lasco fields from the March 7 event and makes the leading edge of the halo difficult to track. The event continues into the C3 field beginning 04:44 to 08:35 UT out to 20 Rsun at last frame before a temporary data gap. Time/height measurements were marked to 4 points in C2 with speeds of 1029.4 Km/sec at position angle 292 degrees. The event is marked to 10 points in C3. Speeds average through both fields to 863.3 Km/sec at PA 292 degrees. Acceleration -40.86 m/sec^2. A second set of measurements were taken over the east. C2 marked at 4 points with speeds of 1157.7 km/sec at pa 78 degrees. C3 marked at 6 points. Averaged speeds through both fields 948.1 km/sec at pa 78. Acceleration of -49.65 m/sec^2. SDO/AIA 193 shows a flare of AR 11429 located at [N17,W03] beginning 03:27-04:33 UT. A symmetric wave and dimming begins at 03:39 UT which spans the front of the disk. STEREO: Beacon data COR2 B, First seen at 04:25 UT with LE at 5.3 Rsun in the west. An expanding loop CME with cavity and core develops to a full asymmetric halo over the west hemisphere. Preliminary time/height measure gives 737.9 km/sec velocity at LE. EUVI B, 03:36-04:26 UT a cme over the west limb. COR2 A, Data gap starts at 03:54 UT. n/a EUVI A, 03:35-03:55 UT (03:55 UT last frame before gap) expanding cme over east limb. NOAA reports a M6.3 Xray flare of AR 11429 03:22-04:18 UT. The observation of this event is considered 'POOR'. 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/2012/120309ab/ Best regards, Kevin Schenk Solar Heliospheric Observatory EIT and LASCO Operations NASA-Goddard Space Flight Center, USA BT