SpaceWeather.com says most solar physicists would likely say that a "puny comet" couldn't set off a "coronal mass ejection" of solar particles.
But check out this video from over the weekend, when a comet struck the sun. The images were animated by Helioviewer.org, "an open-source project for the visualization of solar and heliospheric data" that is funded by the European Space Agency and NASA.
According to SpaceWeather:
"Earlier this year ... the Solar Dynamics Observatory (SDO) watched another sungrazer disintegrate in the sun's atmosphere. On July 5, 2011, the unnamed comet appeared to interact with plasma and magnetic fields in its surroundings as it fell apart. Could a puny comet cause a magnetic instability that might propagate and blossom into a impressive CME? The question is not so crazy as it once seemed to be."