Magnetohydrodynamic Turbulence in a Spherical Shell, Part 2: Emergent Magnetic Field from a Turbulent Geodynamo

Using established results, we examine how a turbulent magnetic field in an outer core emerges and manifests itself as the geomagnetic field. Two basic results are demonstrated: First, how the stationary interior magnetic dipole components gain fluctuating parts, leading to polar wander of the geomagnetic dipole. Second, how the relation between the interior dipole energy ED and magnetic helicity HM, i.e., ED=kminHM, permits us to estimate the value of HM in the outer core from the strength of the geomagnetic dipole field. We also discuss how MHD turbulence with magnetic helicity may be seen as the essential engine of the geodynamo.