What is the name of the Sun's 11-year activity cycle?

The Sun's 11-year activity cycle is called the solar cycle. It is also known as the sunspot cycle or Schwabe cycle, after Heinrich Schwabe, whose observations in the 19th century revealed the repeating pattern in sunspot numbers.

During a cycle, sunspots, solar flares, coronal loops, radiation, and eruptions generally rise from solar minimum to solar maximum and then decline again. The cycle is driven by changes in the Sun's magnetic field, which is generated by moving plasma inside the star.

A common mix-up is the phrase magnetic reversal. The Sun's large-scale magnetic field does reverse near solar maximum, but that reversal is an event within the roughly 11-year solar cycle, not the standard name for the cycle itself. The complete magnetic pattern takes about 22 years to return to its original polarity and is called the Hale cycle.

Solar activity affects space weather, including auroras, radio conditions, satellites, and power systems. Individual cycles are not exactly 11 years long; observed cycles can be shorter or longer.