A bright comet was observed plungin toward the Sun, overheating, and disintegrating by the STEREO (Ahead) COR2 coronagraph (May 22-24, 2008) over about a 36-hour period. The comet was a member of the Kreutz sungrazer family, named after a 19th century German astronomer who studied them in detail. Kreutz sungrazers are fragments from the breakup of a giant comet at least 2000 years ago. Many of these fragments pass by the Sun and disintegrate. Most are too small to see, but occasionally a big comet like this one comes by. (The Sun is represented by the white circle and the black disk is the occulting disk used to block out the immediate area around the Sun so we can see fainter structures in the surrounding corona.)
Even though a faint coronal mass ejection (CME) does occur just as the comet approaches the Sun, this is clearly a coincidence. It occurs before the comet even reaches the Sun. There is no known mechanism for an extremely tiny object like a comet (compared to the huge mass of the Sun) to trigger a magnetic explosion on the Sun, especially across a distance of a million km.