Subject: SOHO/LASCO HALO CME 110924cd

UCMEO 93001 10926 1930/
10924 61948 80306 0321/ 031// 223// 31065
10924 61909 81945 16012 11302 1112/
99999

PLAIN

SOHO/LASCO observed a third asymmetric HALO CME on
September 24, 2011. The event was first seen in C2 at 19:48 UT
with a rough LE front with extensions in the NNE. A full halo
event by 20:36 UT. This continues in the C3 field at 20:06-03:06
UT where it dissipates at 22 Rsun. This appears to be the result of
2 flares close in time.

Time/height measurements were marked at 6 points in C2 showing
614.3 km/sec at PA 55 degrees. The front accelerates in C3
with averaged speeds through both fields of 1065.8 km/sec at 
PA 47 degrees.  

SDO/AIA 193 shows a flare beginning 19:09 - 19:45 UT from AR 11302 in
the NE at [N12, E60]. The flare produced a CME with dimming and wave 
over the north and northwest.  A second flare 20:30-20:48 UT from AR 11302
with CME is most likely associated with the halo in LASCO.
NOAA reports a M3.0 Xray flare of AR 11302 beginning 19:09-19:41 UT and a
M5.8 Xray flare of AR 11302 20:29-20:42 UT.

STEREO COR2 A sees a large loop front over the east/northeast beginning 19:48 UT.
Time/height measurements from COR2 A beacon data at 5 points with speeds of
1245 km/sec at PA 61 degrees.

 
This is most probably the cause of the HALO events seen in LASCO.
   
The observation of this event is considered 'GOOD'. These are determined a FRONTSIDED 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/2011/110924cd/

Best regards,

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

BT