Abstract
The problem of how the small-scale magnetic field generates the large-scale magnetic field has not been completely solved, regardless of many recent MHD dynamo simulations. Usually the process is explained in terms of the local instantaneous alpha-effect, which approximates the electromotive force. It is not, however, obvious whether this approximation is appropriate. We examine the properties of the electromotive force by a kinematic dynamo model with a steady two-dimensional flow. We obtain that the electromotive force for the Earth's core has nonlocal memory effects, which generate magnetic fields stronger than there produced by the local instantaneous alpha-effect.
