I believe it has something to do with the rotation periods of the sun's outer layers. The rotations periods of the sun differ from the poles to the equator, so the magnetic lines get all strung about, until it breaks. Then you have solar flares and coronal ejections and things.
Why they are predominant at the equator.. I'm not completely sure. I think it follows from the rotation period again.
It was shown on a documentary last night. The fact that the sun traveled faster at the equator and the magenetic disturbance showed a predominance of sun spots about its equator. There;s a nasa scientist that has been tracking the rise and fall of sun spots since the 80's and he has it up on his site. The documentary didn't provide a link however it said that many quacks depend on this site for stock/ market predictions.