Sun is the main source of energy for all planets of the solar system. This energy is delivered to Earth in a form of solar radiation in different wavelengths, called total solar irradiance. Variations of solar irradiance lead to heating of upper planetary atmosphere and complex processes of solar energy transport towards a planetary surface.
The signs of solar activity are seen in cyclic 11-year variations of a number of sunspots on the solar surface using averaged monthly sunspot numbers as a proxy of solar activity for the past 150 years. Solar cycles were described by the action of solar dynamo mechanism in the solar interior generating magnetic ropes at the bottom of solar convective zone. These magnetic ropes travel through the solar interior appearing on the solar surface, or photosphere, as sunspots indicating the footpoints where these magnetic ropes are embedded into the photosphere.
Magnetic field of sunspots forms toroidal field while solar background magnetic field forms poloidal field. Solar dynamo cyclically converts poloidal field into toroidal one reaching its maximum at a solar cycle maximum and then the toroidal field back to the poloidal one towards a solar minimum. It is evident that for the same leading polarity of the magnetic field in sunspots in the same hemisphere the solar cycle length should be extended to 22 years.