the variation of sunspots, prominences, flares, and other solar activity through an 11-year cycle.
Why Do We Have Leap Year?Even though the standard calendar year is 365 days, the Earth actually takes 365 days 5 hours 48 minutes and 46 seconds to go completely around the sun. (This is called a solar year.) In order to keep the calendar cycle synchronized with the seasons, one extra day is (usually) added every four years as February 29th. The Julian calendar (established by Julius Caesar in …
Compare sunspot cycle.
Also called solar activity cycle.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019