The problem of magnetic field generation by a flow of electrically conducting fluid parallel to a rigid plate is considered. It is shown that growing magnetic fields occur when the plate exhibits variations of the electrical conductivity in the streamwise direction of sufficient strength. In particular the case of sinusoidal variations is studied. The magnetic Reynolds number for dynamo action increases with decreasing conductivity of the plate and with decreasing amplitude of its modulation. Possible applications to geophysical problems are discussed.
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