THE ELECTROMAGNETIC FIELD WITHIN A DISCONTINUOUS CONDUCTOR WITH REFERENCE TO GEOMAGNETIC MICROPULSATIONS NEAR A COASTLINE

Abstract

The two-dimensional problem of a low-frequency, plane-polarized electromagnetic wave incident on a semi-infinite conducting medium with a plane surface is treated for the case when the medium has a discontinuity, the regions on either side of a plane normal to its surface being of different conductivities. Arguments are given to show that it is reasonable to assume, as a low-frequency approximation, that the tangential magnetic field is constant on the surface of the conductor. With the aid of this approximation, solutions are obtained for the two cases when (i) the magnetic vector (H polarization) and (ii) the electric vector (E polarization) is always parallel to the trace of the discontinuity.The model is discussed with reference to the behavior of geomagnetic micropulsations near a coastline, particular attention being paid to the E-polarization solution which contains a magnetic component normal to the surface of the conductor. The amplitude of this component at the surface is shown to increase sharply as the region of the discontinuity is approached, thus providing an explanation of the enhanced Z magnetic component in the micropulsation field observed at coastal stations.