Sunspot Cycle

Eleven-year periodicity in the number of sunspots observed on the Sun. Sunspot maxima are associated with times of high solar activity (many flares and solar storms). During sunspot minima, there may be no spots visible on the Sun for several days. The number of sunspots present during the maxima varies with each cycle. The 1958 maxima showed the highest sunspot activity on record. There were very few sunspots from 1645-1715, even during the maxima. This interval is called the “Maunder Minimum,” and represented a period of solar inactivity that probably caused  the “Little Ice Age” on Earth.


Image source: http://www.theresilientearth.com/?q=content/little-ice-age-ii-sequel