The phrase "activity cycle" refers to a repeating pattern of actions or events that happen in a particular order. It describes the sequence of activities or tasks that are regularly performed. Full definition
- Climate change throughout human history closely follows solar activity cycles. (patch.com)
This determines the long - term trend in the solar variability, which is then superposed with the 11 - year activity cycle calculated from the sunspot number. (aanda.org)
No. 1 Sun Beneath the Earth: Solar Activity Cycles in Tropical Caves Are Revealed Translated by P Gosselin (notrickszone.com)