Why does the Sun have an 11-year activity cycle?

The Sun goes through periods of high and low activity because its magnetic field is constantly being twisted by the flow of hot plasma inside it. Roughly every 11 years, the number of sunspots rises to a maximum and then falls again, although the full magnetic cycle lasts about 22 years because the field reverses polarity and returns to its original orientation. This cycle affects solar flares, coronal mass ejections, and space weather near Earth. Solar-cycle studies have been tracked for centuries, with telescopic sunspot observations beginning in the early 1600s.