In this paper , we present multiwavelength observations of helical kink instability as a trigger of a CME which occurred in AR NOAA 11163 on 24 February 2011 .
The CME was associated with a M3.5 limb flare .
High resolution observations from SDO/AIA suggest the development of helical kink instability in the erupting prominence , which implies a flux rope structure of the magnetic field .
A brightening starts below the apex of the prominence with its slow rising motion ( \sim 100 km s ^ { -1 } ) during the activation phase .
A bright structure , indicative of a helix with \sim 3-4 turns , was transiently formed at this position .
The corresponding twist of \sim 6 \pi -8 \pi is sufficient to generate the helical kink instability in a flux rope according to recently developed models .
A slowly rising blob structure was subsequently formed at the apex of the prominence , and a flaring loop was observed near the footpoints .
Within two minutes , a second blob was formed in the northern prominence leg .
The second blob erupts ( like a plasmoid ejection ) with the detachment of the northern prominence leg , and flare intensity maximizes .
The first blob at the prominence apex shows rotational motion in the counterclockwise direction in the plane of sky , interpreted as unwinding motion of a helix , and it also erupts to give the coronal mass ejection ( CME ) .
RHESSI hard X-ray sources show the two footpoint sources and a loop-top source during the flare .
We found RHESSI hard X-ray flux , soft X-ray flux derivative and CME acceleration in the low corona correlate well , which is in agreement with the standard flare model ( CSHKP ) .
We also discuss the possible role of ballooning as well as torus instabilities in driving the CME .
We conclude that the CME and flare were triggered by the helical kink instability in a flux rope and accelerated mainly by the torus instability .