Gnevyshev–Ohl rule

The Gnevyshev–Ohl rule is an empirical relationship that describes the relationship between solar activity, specifically sunspot cycles. It was formulated by the Russian astronomers Mikhail Gnevyshev and Alexander Ohl in the 1940s. The rule states that during a solar cycle, the amplitude (or peak number) of the next sunspot cycle tends to be higher if the previous cycle had a particularly low or below-average amplitude.