Spörer's law
In solar physics, Spörer's law is an empirical law for the variation of heliographic latitudes at which solar active regions form during a solar cycle. It was discovered by the English astronomer Richard Christopher Carrington around 1861. Carrington's work was refined by the German astronomer Gustav Spörer. At the start of a solar cycle, active regions tend to appear around 30° to 45° latitude on the Sun's surface. As the cycle progresses, they appear at lower and lower latitudes, until they average 15° at solar maximum.