Solar Activity Cycle

The solar cycle, or solar magnetic activity cycle, is a nearly periodic 11-year change in the Sun’s activity. Generally speaking, with each cycle, the Sun’s north and south poles trade places. Levels of solar radiation and ejection of solar material, the number and size of sunspots, solar flares, and coronal loops all exhibit a synchronized fluctuation, from active to quiet to active again, with a period of about eleven years. This cycle has been observed for centuries by changes in the Sun’s appearance and by terrestrial phenomena such as auroras.
The changes on the Sun cause effects in space, in the Earth’s atmosphere, and on Earth’s surface. While the cycle is the dominant influence on solar activity, aperiodic fluctuations also occur.

Solar activity cycle from 1749 to today