Evidence of a blast shock wave formation in a “CME-streamer” interaction

Analysis of the solar event on 16 February 2011 (SOL2011-02-16T14:19) allows to classify it as an “impulsive” coronal mass ejection (CME) event. It is argued that the observed deviation of a streamer ray from its pre-event state and generation of a metric type II radio burst in this event was a result of a “CME-streamer” interaction in the lower corona (r≲1.5R⊙). Most probably, it was a consequence of an impulsive action of a compressed magnetic field to the streamer. This compression of the coronal magnetic field was due to a moving and expanding magnetic flux rope, which was a core of the CME. The estimated radial speed of the type II burst sources was significantly (≈2-8 times) larger than the radial speed of the erupting flux rope, and it decreased rapidly with time. This indicates that during the “CME-streamer” interaction a blast shock wave could be excited and propagated along the streamer.