- The 22-year period over which the pattern of sunspots on the Sun’s surface repeats itself. The solar cycle was long thought to last 11 years, but analysis of sunspot records shows that the 11-year peaks seem to come in pairs, so that a 22-year cycle is now often thought of as being more correct. Many attempts have been made to find possible longer cycles of several 22-year periods. There have also been lengthy periods in the 300-year-plus history of solar observation when few if any sunspots have been visible.
- The solar cycle, the 22-year period over which sunspot activity varies
- The periodic variation in the number of sunspots, and in the levels of other solar activity, such as solar flares. Each cycle lasts approximately eleven years. Also called sunspot cycle.
- synonym sunspot cycle
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