Subject: SOHO/LASCO HALO CME 120919ab BACKSIDED

UCMEO 93001 20919 1930/
20919 61148 91554 0892/ 088// 223// 30542
20919 61105 81306 ///// ///// 1112/
99999

PLAIN

SOHO/LASCO observed  two HALO CMEs on September 19, 2012 in close succession.
The first event is seen in C2 at 11:48 UT with a bright loop over the equatorial east.
The event is a full halo by 12:36 UT.  The second event is in close progress at 13:25 UT
with loops expanding over the north and east and a full halo by 15:12 UT.
The event continues into the C3 field beginning 12:18 to 15:54 UT at last frame in C3
before a DSN data gap out to 18 Rsun in the Southeast.

Time/height measurements were marked for the first event [A] to 5 points in C2 with speeds 
of 611.3 Km/sec at position angle 98 degrees. The event is marked to 11 points 
in C3. Speeds average through both fields to 510.2 Km/sec at PA 98 degrees.  
Acceleration -22.03 m/sec^2.

Time/height measurements were marked for the second event [B] to 7 points in C2 with speeds
of 439.0 Km/sec at position angle 23 degrees. The event is marked to 9 points  
in C3. Speeds average through both fields to 542.0 Km/sec at PA 23 degrees.   
Acceleration 19.08 m/sec^2.


SDO/AIA:  Eclipse period 06:06-07:24 UT.
304A shows a CME in progress first frame after eclipse at 07:21 UT.  This is partial emission
from an un-numbered AR at limbs edge [N24, E78].  A large spray of material is seen from behind
the North and East limbs beginning 13:03 UT. 
193 shows a darkening of material 12:06-16:15 UT Near the east limb [N5, E59] west of AR 11575
which is now on the east limb.

STEREO: Beacon data
COR2 B, 11:40 UT a burst over the SE.  At 13:55 UT expanding large loop over east hemisphere.
Event [B] : Preliminary time/height measure gives 662.3 km/sec velocity at LE.
EUVI B, eclipse 10:36-11:26 UT.  11:36 UT, cme in progress from AR on disk in SE. At 12:06-12:56 UT
a large flare of the region with wave.
COR2 A, 11:24 UT emission to the SW.  Beginning 12:54 UT a partial halo of expanding loops over the 
north and west hemispheres.
Event [A]: Preliminary time/height measure gives 977.1 km/sec velocity at pa 254.
Event [B] : Preliminary time/height measure gives 504.4 km/sec velocity at pa 293.
EUVI A, 11:05-11:45 UT a flare of AR near limb in SW.  12:15-13:05 UT a flare of a different region in SW
above the 11:05 UT event.

   
The observation of this event is considered 'FAIR'. This CME is determined a BACKSIDED event. This
multi-part event is shown with small areas of material over the limb.

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

http://umbra.nascom.nasa.gov/lasco/observations/halo/2012/120919ab/

Best regards,

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

BT