The sun is governed by a strict rhythm. The magnetic activity of the sun displays a cyclic variation, reaching a maximum approximately every eleven years. Two enormous plasma circulations, each in one solar hemisphere, set the pace for this rhythm, thus defining the sun's eleven-year cycle. Near the surface, the plasma flows carry the magnetic field lines from the equator to the poles; in the solar interior, the plasma flows back to the equator in a huge cycle spanning the entire hemisphere.