Subject: SOHO/LASCO HALO CME 140418ab

UCMEO 93001 40418 1930/
40418 61325 81742 1771/ 170// 333// 41208
40418 61233 81318 33118 12036 1112/
99999

PLAIN

SOHO/LASCO observed two (2) HALO CMEs in close succession April 18, 2014.  
The events are first seen in C2 at 13:25 UT as a bright loop in progress
over the Southwest.  The front expands with extensions to a full HALO CME
by 13:36 UT. The event continues into the C3 field beginning 13:30 to 17:42 UT
leaving the C3 field of view at 30Rsun in the South.  Increased proton
flux is seen in the Lasco fields.

Event (A): (asymmetric halo)
Time/height measurements were marked to 2 points in C2 with speeds of 1320.0 Km/sec
at position angle 177 degrees.  The event is marked to 8 points in C3. Speeds average
through both fields to 1208.3 Km/sec at PS 177 degrees. Acceleration -48.47 m/sec^2.

Event (B): (partial halo)
Time/height measurements were marked to 3 points in C2 with speeds of 1168.4 Km/sec
at position angle 234 degrees. The event is marked to 8 points in C3.  Speeds average
through both fields to 1202.7 Km/sec at PA 234 degrees.  Acceleration -41.37 m/sec^2.

SDO/AIA 193A (A) shows a CME beginning 12:33 UT from AR 12036 at location [S18, W31]. A flare
of the region starts 12:51-13:18 UT producing a dimming of the South and West hemispheres
and a wave.  
SDO/AIA 304 (B) shows activation of a filament centered at location [S23, W30], South of 
AR 12036 beginning 05:24 UT.  Eruption of the filament begins 06:51-07:57 UT with
ribbon flaring of the area and along transient lines of the AR. Impulsive flare of
the AR follows at 12:45 UT. 

STEREO: BEACON Data
COR2 A, 13:24-14:54 UT, asymmetric HALO over the East.  
Preliminary time/height measure gives 1217.8 km/sec velocity at LE. 
EUVI A, n/a
COR2 B, 13:25-15:40 UT, Partial HALO CME over the South.
Preliminary time/height measure gives 753.1 km/sec velocity at LE.
EUVI B, n/a

NOAA reports a M7.3 class X-ray LDE flare from AR 12036 beginning 12:31 UT.
   
The observation of this event is considered 'GOOD'. This CME is determined a 
FRONTSIDE

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

http://umbra.nascom.nasa.gov/lasco/observations/halo/2014/140418ab/

Best regards,

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

BT