Subject: SOHO/LASCO Partial HALO CME 110725 BACKSIDED

UCMEO 93001 10725 1730/
10725 61812 80506 0122/ 011// 113// 30285
10725 61515 ///// ///// ///// 3222/
99999

PLAIN

SOHO/LASCO observed a full HALO CME on July 25, 2011.  Event is first seen in
C2 at 18:12 UT as small loops on the north at 12 and on the south at 188 degrees. 
The occulter was engulfed by 18:48 UT with material at all PAs.
The event continues into the C3 field beginning 19:42 UT to 05:06 UT out to
17.44 Rsun where the event dissipates.

Time/height measurements were marked to 10 points in C2 with speeds of 329.3 Km/sec
at position angle 93 degrees. The event is marked to 9 points in C3 where it
slightly decelerates.  Speeds average through both fields to 285.3 Km/sec at
PA 88 degrees. Acceleration of  -2.77 m/sec^s. 

STEREO COR2 B shows a large cme beginning 17:40 UT in the East field.
EUVI 195 A shows elevated filament material in the SW and W field at 15:15 UT
which does erupt.
SDO/AIA does not show any evidence of the event on disk.  In difference images
there is evidence of flows from the backside beginning 16:27 UT. 

These events are most probably the cause of the HALO event seen in LASCO.

The observation of this event is considered 'FAIR'. 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/2011/110725/


Best regards,

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

BT