  A series of numerical simulations of the dynamo process operating inside gas
giant planets has been performed. We use an anelastic, fully nonlinear,
three-dimensional, benchmarked MHD code to evolve the flow, entropy and
magnetic field. Our models take into account the varying electrical
conductivity, high in the ionised metallic hydrogen region, low in the
molecular outer region. Our suite of electrical conductivity profiles ranges
from Jupiter-like, where the outer hydrodynamic region is quite thin, to
Saturn-like, where there is a thick non-conducting shell. The rapid rotation
leads to the formation of two distinct dynamical regimes which are separated by
a magnetic tangent cylinder - mTC. Outside the mTC there are strong zonal
flows, where Reynolds stress balances turbulent viscosity, but inside the mTC
Lorentz force reduces the zonal flow. The dynamic interaction between both
regions induces meridional circulation. We find a rich diversity of magnetic
field morphologies. There are Jupiter-like steady dipolar fields, and a belt of
quadrupolar dominated dynamos spanning the range of models between Jupiter-like
and Saturn-like conductivity profiles. This diversity may be linked to the
appearance of reversed sign helicity in the metallic regions of our dynamos.
With Saturn-like conductivity profiles we find models with dipolar magnetic
fields, whose axisymmetric components resemble those of Saturn, and which
oscillate on a very long time-scale. However, the non-axisymmetric field
components of our models are at least ten times larger than those of Saturn,
possibly due to the absence of any stably stratified layer.
