SOHO/LASCO HALO CME 120407ab BACKSIDED

UCMEO 93001 20409 2030/
20407 61648 82230 2872/ 286// 323// 30588
20407 71625 91655 ///// ///// /////
99999

PLAIN

SOHO/LASCO observed two (2) halo HALO CMEs on April 7, 2012.  Event is first
seen in C2 at 16:48 UT as a loop on the west limb. The loop with cavity and
core material expands with extensions to a full asymmetric halo cme by 17:24 UT.
A second event following is seen in C2 beginning 21:15 UT. The system expands
with extensions as a partial halo 198 degrees wide from  pa 014-212 degrees.
The event continues into the C3 field beginning 17:06 to 22:30 UT where is
dissipates at 25 Rsun in the west. Beginning at 21:54 UT the slow multi-loop
system over the south expands where it leaves the C3 field at 05:42 UT. 

Time/height measurements were marked [20120407a] to 4 points in C2 with speeds of 1091.3 Km/sec
at position angle 261 degrees. The event is marked to 12 points in C3.  Speeds average
through both fields to 791.0 Km/sec at PA 260 degrees.  Acceleration -44.04 m/sec^2.
Measurements were marked [20120407b] to 5 points in C2 with speeds of 604.2 at pa 168
and 12 points in C3.  Speeds averaged through both fields to 757.5 km/sec at pa 170.
Acceleration of 30.98 m/sec^2.


SDO/AIA 193 shows a CME event behind limb 20:18-00:33 UT seen in difference images
over the SE and South.
AIA 304 shows rising prominence material over the NE limb 15:36-17:39 UT.  From 20:42-21:42 UT
a loop cme is seen from backside over the south pole area. 

STEREO: Beacon data
COR2 A, 13:54-19:24 UT data gap.  21:54-03:54 UT data gap.  At 03:54 UT a wide expanding
loop in progress over south hemisphere. 
EUVI A, 14:05-19:15 UT data gap. In progress at 19:35 UT a wide prominence erupting.
21:55-03:55 UT data gap.
COR2 B, 16:39 UT loop over east expanding SE.  
20:24-22:54 UT data gap. At 22:54 UT a cme over the SE field (in light eclipse period).
Preliminary time/height measure gives 1057.5 km/sec velocity at pa 97 degrees.
EUVI B, 15:45-16:25 UT data gap. in progress at 16:25 a cme from AR on east limb.
19:55-23:45 UT data gap. in progress at 23:45 UT a filament eruption on disk in the SE
near the limb till a data gap from 02:05-03:45 UT.

   
The observation of this event is considered 'FAIR'. Both events are determined BACKSIDED events.

Images and movies and time/height information for this event is available on the web at:

http://umbra.nascom.nasa.gov/lasco/observations/halo/2012/120407ab/

Best regards,

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

BT