A NONLINEAR MODEL OF THE SOLAR DYNAMO

The role of nonlinearity is explored in a mean-field dynamo model. Magnetic fields are amplified by the combined action of the alpha and omega-effects, and as the field's intensity increases the Lorentz force becomes important. Torsional oscillations and meridional circulations are driven by the Lorentz force, and the oscillations are consistent with those measured on the surface of the Sun. The torsional oscillations feedback in the induction equation and saturate the magnetic field's growth by quenching differential rotation. This model can also help us understand the processes responsible for the range of periods seen in the activity cycles of other stars like the Sun.