Hello,

I think this is highly unlikely. First, coronal mass ejections (CMEs) and other solar storms actually happen fairly often. The asteroid belt objects have probably encountered thousands of CMEs over the lifetime of the solar system, without this ever happening. While CME plasma can have higher density and temperature than the normal solar wind, the CME plasma is still not very dense at all compared to an asteroid. It does not seem likely to me that a CME could suddenly heat up an asteroid to the point of exploding. Even if an asteroid were to explode for some other reason, I don't think the "shrapnel" from it would cause a chain reaction that pushes a larger object onto a collision course with Earth. The reason why not is conservation of momentum. While pieces of asteroid "shrapnel" from an explosion could be moving very fast, the individual fragments would probably be small and not have a lot of mass. Therefore, individual fragments would not have enough momentum to push a larger, much more massive object out of its orbit. The asteroids are actually very far apart, and fragments from an asteroid explosion would probably be very spread out before they reached another object.

Kris