The solar cycle, also known as the solar magnetic activity cycle, sunspot cycle, or Schwabe cycle, is a nearly periodic 11-year change in the Sun's activity measured in terms of variations in the number of observed sunspots on the Sun's surface. Over the period of a solar cycle, 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 a period of minimum activity to a period of a maximum activity back to a period of minimum activity.
The magnetic field of the Sun flips during each solar cycle, with the flip occurring when the solar cycle is near its maximum. After two solar cycles, the Sun's magnetic field returns to its original state, completing what is known as a Hale cycle.
This cycle has been observed for centuries by changes in the Sun's appearance and by terrestrial phenomena such as aurora but was not clearly identified until 1843. Solar activity, driven by both the solar cycle and transient aperiodic processes, governs the environment of interplanetary space by creating space weather and impacting space- and ground...