Subject: SOHO/LASCO Partial HALO CME 110326 BACKSIDED

UCMEO 93001 10331 1630/
10326 60612 81354 2362/ 235// 113// 30360
///// ///// ///// ///// ///// /////
99999

PLAIN

SOHO/LASCO observed a Partial HALO CME on March 26, 2011.  Event is first seen in
C2 at 06:12 UT as a multiloop, multilayer system following a large impulsive burst
from the east limb.  (The burst may possibly be a trigger).  The front expands with
extensions.  By 09:12 there is faint material scattering at all positions.  A single
very faint line over the South pole region by 08:12 UT, expansion seems uniform and
is considered part of the event. This event should still be considered a partial HALO
due to multi part events.  The event continues into the C3 field beginning 07:30 UT
to 13:54 UT at 15.0 Rsun.

Time/height measurements were marked to 11 points in C2 with speeds of 335.5 Km/sec
at position angle 6 degrees. The event is marked to 16 points in C3 where it
slightly accelerates.  Speeds average through both fields to 360.2 Km/sec at
PA 4 degrees.  Acceleration of 2.64 m/sec^2.

STEREO EUVI 195 B shows a filament eruption beginning 04:55 off the East limb
at equator line.  At 05:05 UT it appears a dual ribbon flare with signatures of AR 
in the NW, along with post loop arcade. At 08:00 UT a flare of the small AR on the
NW limb with cme.
EUVI 195 A shows a cme at 05:10 on the NW near equator over limb. At 08:00 UT a
small cme on the NE limb.  At 09:15 UT a small flare of AR in NE quadrant.
EUVI 304 B shows a filament eruption prior to a flare of the AR beginning 04:46 UT.
STEREO COR2 B shows a large CME at 06:24 in the NE with a partial halo beginning 07:24 UT.
SDO/AIA 193 sees a cme from the AR 11180 near the NE limb beginning 05:09 UT.
These events together are most probably related with the obscure 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/2011/110326/


Best regards,

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

BT