Some new results on spherical dynamos

Small-scale motions in the Earth's liquid core are likely to be highly anisotropic because of the effects of rotation. Guided by physical considerations, the “-effect” described by an anisotropic tensor _ik is formulated and the corresponding boundary value problem for a sphere is solved for a variety of boundary conditions. A converged solution has been obtained only in the case of the Fermi condition of an infinitely conducting exterior of the sphere. In a second part of the paper, some remarks are made on the hypothetical upper bound on magnetic field strengths in planetary cores originally proposed by Busse (1976).