  To explain the large-scale magnetic field of the Sun and other bodies,
mean-field dynamo theory is commonly applied where one solves the averaged
equations for the mean magnetic field. However, the standard approach breaks
down when the scale of the turbulent eddies becomes comparable to the scale of
the variations of the mean magnetic field. Models showing sharp magnetic field
structures have therefore been regarded as unreliable. Our aim is to look for
new effects that occur when we relax the restrictions of the standard approach,
which becomes particularly important at the bottom of the convection zone where
the size of the turbulent eddies is comparable to the depth of the convection
zone itself. We approximate the underlying integro-differential equation by a
partial differential equation corresponding to a reaction-diffusion type
equation for the mean electromotive force, making an approach that is nonlocal
in space and time feasible under conditions where spherical geometry and
nonlinearity are included. In agreement with earlier findings, spatio-temporal
nonlocality lowers the excitation conditions of the dynamo. Sharp structures
are now found to be absent. However, in the surface layers the field remains
similar to before.
