Final answer:
The sunspot cycle extends over 22 years due to the reversal of magnetic polarity after every 11-year cycle, making two cycles necessary for a full repetition. This is linked to the behavior of the Sun's magnetic field, involving differential rotation and convection below the solar surface.
Step-by-step explanation:
The sunspot cycle is actually 22 years long because during each 11-year cycle, the magnetic polarity of sunspots reverses. While the number of visible sunspots varies according to an average cycle of 11 years, the polarity of the leading sunspots in each hemisphere switches after one 11-year cycle. Therefore, the magnetic activity cycle of the Sun lasts for 22 years, as it takes two of these 11-year cycles for the entire sunspot cycle, including the magnetic polarities, to repeat itself.
Magnetograms visually represent the Sun's magnetic fields and show the relationship between sunspots and the Sun's magnetic field, illustrating this 22-year cycle. The complex nature of solar activity is driven by the Sun's changing magnetic field, which includes differential rotation and convection processes that twist and distort magnetic fields, causing them to strengthen, decay, and eventually regenerate with opposite polarity every approximately 11 years. This process leads to the 22-year cycle due to the polarity reversal.