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sunspot cycle

The roughly 11-year cycle during which the frequency of sunspots varies from a maximum to a minimum level and back again. During a given sunspot cycle, the leading sunspots in groups in the northern solar hemisphere all tend to have the same polarity, while the same is true of sunspots in the southern hemisphere, except that here the common polarity is reversed. During the next sunspot cycle, the leading spots in each hemisphere flip to the opposite polarity. From this it's clear that the fundamental period governing solar activity is actually the 22-year magnetic cycle.

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