A hydromagnetic αω-dynamo is investigated based on a simple, nearly homogeneous, isotropic and mirror-symmetric turbulence. An upper bound on the magnetic field in the core is derived by considering both the actions of the Coriolis and magnetic forces. It is unlikely that αω-dynamo produces a toroidal magnetic field larger than 30 gauss. Then the poloidal field in the core hardly exceeds 10 gauss.
From considerations of energy balance the possible ranges of the characteristic length scale and the intensity of turbulence in the core are also estimated. It follows that the scale of turbulence must be larger than 10km and the intensity must be smaller than 5×10-3cm/sec so that energy dissipation due to Joule heat may not exceed the possible energy available for the geodynamo.