The polarity of Northern Hemisphere sunspots are opposite to those in the Southern Hemisphere. If the magnetic polarity of the inital sunspots in a cycle are "northern" the later sunspots in that cycle will form with increasing "southern" polarity (Hale's sunspot polarity law). This will be reversed in the next 11 year cycle. The following 11 year cycle (22 years from the initial cycle) will have sunspots will similar polarity to the initial cycle. From a physical standpoint, the true length of the solar cycle is not 11 years, but rather 22 years. This has been shown to be caused by the magnetic poles of the sun rotating in a 22 year cycle.