The fact that the Suns outer layers are bubbling, and that the Sun rotates faster at the equator than the poles, and faster on the inside than on the surface, results in a solar dynamo that, over 11 years, becomes increasingly wound up. So at some stage during the magnetic cycle the Sun has to somehow shed its old, contorted magnetic skin, and allow a newer, less troubled one, to emerge.
http://news.bbc.co.uk/1/hi/sci/tech/3226844.stm
