Subject:  SOHO/LASCO Partial HALO CME 110907a BACKSIDED

UCMEO 93001 10908 1930/
10907 61848 80054 2782/ 157// 323// 40959
10907 61826 81836 ///// ///// 1222/
99999

PLAIN

SOHO/LASCO observed a Partial HALO CME on September 7, 2011.  Event is first seen in
C2 at 18:48 UT as bright loop with cavity and core centered at 50 degrees in the NE.
The front expands with extensions PA 278-157 degrees for a total coverage of 239
degrees wide.  The event continues into the C3 field beginning 19:18 to 00:54 UT to 27 Rsun.

Time/height measurements were marked at 4 points in C2 with speeds of 1020.9 Km/sec
at position angle 69 degrees. The event is marked to 6 points in C3 where it
slightly slows.  Speeds average through both fields to 959.0 Km/sec at PA 68 degrees.
Acceleration of -4.86 m/sec^s.

SDO/AIA 193 shows a flare of AR 11289 in the NE [N23, E54] 18:27-1930 UT.  There is
a small emission from this flare but the bulk of the cme seen is behind the limb.
STEREO EUVI B beacon data shows a flare with dimming on the NE 18:26-18:36 UT. There
is a data gap 18:36-23:26.
COR2 A cme beginning 18:54 UT in the west, almost a halo. This could indicate possible
emission frontside.
Preliminary time/height measurements using COR2 A beacon data gives speeds of 845.7 k/sec.

This is most probably the cause of the Partial 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/2011/110907a/

Best regards,

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

BT