Subject:  SOHO/LASCO Partial HALO CME 110908 BACKSIDED

UCMEO 93001 10909 1715/
10908 62212 80432 2142/ 089// 323// 41104
10908 62145 82205 ///// 11280 1112/
99999

PLAIN

SOHO/LASCO observed a Partial HALO CME on September 8, 2011.  Event is first seen in
C2 at 22:12 UT as loop with cavity and core centered at 318 degrees in the NE.
The front expands with extensions PA 214-89 degrees for a total coverage of 235
degrees wide.  The event continues into the C3 field beginning 23:18 to 04:32 UT to 30 Rsun.

Time/height measurements were marked at 4 points in C2 with speeds of 10245.1 Km/sec
at position angle 320 degrees. The event is marked to 10 points in C3 where it
slightly slows.  Speeds average through both fields to 1104.4 Km/sec at PA 230 degrees.
Acceleration of -2.17 m/sec^s.

SDO/AIA 193 shows backside emission over the NW beginning 21:48 UT.
STEREO EUVI A beacon data shows a flare with north wave on the NW 21:45-22:05 UT likely
from AR 11280(?)  There is a data gap 22:05-23:25 UT which shortens the observation.
COR2 B cme beginning 22:40 UT in the east northeast.
Preliminary time/height measurements using COR2 B beacon data gives speeds of 1077.1 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/2011/110908/

Best regards,

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

BT