Final answer:
On average, sunspot maxima occur every 11 years, influenced by the magnetic activity of the Sun, which has a full cycle of 22 years including polarity reversals. This solar cycle affects the number and appearance of sunspots, as well as solar energy output.
Step-by-step explanation:
Sunspot maxima are known to occur on average every 11 years, but this can vary between as few as 9 years to as many as 14 years. During a sunspot maximum, it is common to observe over 100 sunspots at a time. The cause of the solar cycle, which encompasses the sunspot cycle, is related to the Sun's magnetic activity.
The solar cycle shows variability in the number of sunspots and the Sun's energy output. The magnetic activity cycle of the Sun actually spans about 22 years, because it includes a polarity reversal of the sunspot's magnetic fields from one 11-year sunspot cycle to the next, making the full magnetic cycle double the length of the sunspot cycle itself.
Hence, the solar cycle is characterized not only by the number of sunspots but also by magnetic phenomena and changes in solar energy output that could potentially influence Earth's climate.