The solar magnetic field exhibits a 22-year cycle manifested by the
sunspots. The cycle arises from the dynamo process that maintains the
large-scale magnetic field. It is shown that essential ingredients for
the solar dynamo are large-scale flows (differential rotation,
meridional flows), and turbulence affected by rotation (turbulent
alpha-effect). A standard axisymmetric model working in a 2D spherical
shell and making use of the equations of mean-field magnetohydrodynamics
is presented along with a few representative results. Such models may help
to predict the strength of the next solar maximum. Such predictions
have become critical in deciding about space missions (for example whether
it is advisable to pay for maintenance of the Hubble Space Telescope!)
Empirically one knows that the strength of the so-called dipole moment
during the declining phase of the previous cycle is related to the strength
of the following maximum. Recently solar dynamo models have been used
to make predictions about Solar Cycle 24 (maximum due around 2012) with
rather different outcomes. These techniques will be reviewed and their
respective merits and deficiencies discussed.
