Subject: SOHO/LASCO HALO CME 111103ab

UCMEO 93001 11104 1730/
11103 72312 90042 0791/ 080// 133// 21349
///// ///// ///// ///// ///// /////
99999

PLAIN

Update of explanation to this multipart event.  The event name was changed to
111103ab to show the presence of 2 halo CMEs in this notice.  I should have done
this in the beginning to separate the 2 events better.  The start times for both
events in C2 and C3 remain the same.  The change of the regions which caused the
HALOs determine a BACKSIDED event.  The X1.9 flare was not involved.  Once the
full resolution SECCHI data is available we can correctly identify the sources.

SOHO/LASCO observed an asymmetric HALO CME on November 3, 2011.  Event is first
seen in C2 at 23:12 UT as a full halo in progress with LE at 6 Rsun, edge of the
C2 FOV.  The event continues into the C3 field beginning 23:06 to 00:42 UT. The
last frame of C3 before an unrecoverable data gap out to 15.3 Rsun. There is 2
LE loop systems in C3.  The system leading and covering more of the East/South East
is considered to be the event alert.  

Time/height measurements were marked to 7 points in C3 field only with speeds
of 1349.2 Km/sec at position angle 79 degrees. Acceleration of 59.7 m/s^2.

SDO/AIA shows a flare of AR 11339 20:18-20:39 UT located on disk at[N22,E63].
There was a data gap 20:51-00:00 UT, no dimming or wave seen with the flare.

COR2 A 20:54 UT a faint emission in the North and NE and dissipates.
	22:39-00:39 UT large loop expanding to a halo in the NW field.
	This CME seen is a backside event.  Timings are close but most likely
	pertain to second system.
	time/height: 1024.5 km/sec @247 degrees.
COR2 B data gap 17:40-22:40 UT. Again, no evidence for a frontside CME.
	 Large loop system as a halo in NE which most likely is second system.
	time/height: 924.6 km/sec @88 degrees.
EUVI 195 A shows 22:05 UT with large CME over limb in the NW. Nothing is seen
earlier on the NE at the 20:00-20:30 timerange.
EUVI 195 B data gap 17:46-22:46 UT and missed the timings for the X1.9 flare.

   
The observation of this event is considered 'POOR'. These CMEs are determined BACKSIDED events.

Images and movies and time/height information for this event is available on the web at:

http://umbra.nascom.nasa.gov/lasco/observations/halo/2011/111103/

Best regards,

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

BT