Hi Richard,

The link below goes to a web page that describes how the latitude of sunspot occurence varies with the cycle. It describes how sunspots emerge closer to the poles during the beginning of the cycle, but usually within a belt between -35 and 35 degrees, leading to the butterfly diagram.

Several models have been developed to explain this pattern, but the real reson is unknown. What do you mean exactly by "the magnetic effect of the sun"? One could say that the physics of the magnetic field of the Sun can explain why sunspots don't emerge closer to the poles.

Mandy

http://www.windows2univer...ivity/butterfly.html