Subject: SOHO/LASCO Partial HALO CME 110427 BACKSIDED

UCMEO 93001 10428 2230/
10427 60748 81806 2462/ 131// 333// 40469
10427 60605 80805 ///// ///// 2212/
99999

PLAIN

SOHO/LASCO observed a Partial HALO CME on April 27, 2011.  Event is first seen in
C2 at 07:48 UT as a bright multilayer loop system with a defined cavity and core 
over the Northwest limb centered at PA 320 degrees. The event expands with extensions
over the Northeast.  Material spans PA 246-131 degrees for a total coverage
of 245 degrees over the north hemisphere. The event continues into the
C3 field beginning 08:42 UT to 18:06 UT out to 23.4 Rsun.

Time/height measurements were marked to 6 points in C2 with speeds of 617.1 Km/sec
at position angle 313 degrees. The event is marked to 12 points in C3 where it
slows.  Speeds average through both fields to 469.4 Km/sec at PA 310 degrees.
Acceleration of -12.09 m/sec^2.

STEREO COR2 B shows a large cme beginning 08:39 UT in the NE field expanding north.
COR2 A shows a cme at 07:54 UT in the NW field.
EUVI 195 A shows elevated filament material and dimming in the NE field at 06:05-08:05 UT.
The filament eruption finishes with a bright post arcade.
SDO/AIA 304 shows backsided activity over the limb at 07:13-08:27 UT.

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

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/2011/110427/


Best regards,

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

BT