  Possibilities and difficulties of applying the theory of magnetic field
generation by convection flows in rotating spherical fluid shells to the Giant
Planets are outlined. Recent progress in the understanding of the distribution
of electrical conductivity in the Giant Planets suggests that the dynamo
process occurs predominantly in regions of semiconductivity. In contrast to the
geodynamo the magnetic field generation in the Giant Planets is thus
characterized by strong radial conductivity variations. The importance of the
constraint on the Ohmic dissipation provided by the planetary luminosity is
emphasized. Planetary dynamos are likely to be of an oscillatory type, although
these oscillations may not be evident from the exterior of the planets.

Earth and Planetary Astrophysics;Fluid Dynamics;Space Physics