Relations between Electrical Conductivity of a Mantle and Fluctuating Magnetic Fields

Abstract

It is shown that the ratio of the vertical field to the horizontal field gradient outside a geological body can often be used to measure the electrical conductivity at depth within it. The in-phase part of this ratio, at a given frequency, gives the penetration depth of the magnetic field, the out-of-phase component yields approximately the conductivity at the penetration depth.