Fields of a subsurface conductor buried in close proximity to the interface

The determination of the propagation constants and fields for conductors embedded in a lossy half-space is of interest in low frequency radio transmission, remote sensing applications in geoelectromagnetics, and in the power engineering field for buried cable analysis. It is important to be able to determine the effect of the interface on the propagation and radiation characteristics of the geometry. In the past, almost all theories have treated the problem assuming a thin-wire approximation and/or a uniform axial current distribution to model the conductor. Under the thin-wire approximation, only axially directed currents with a uniform aztmuthal distribution are assumed. Under the uniform axial current assumption, there is no variation of the currents or fields in the axial dimension and thus only conduction currents in the earth are considered with displacement current effects being neglected. In this paper the validity of these approximations are examined by formulating the problem allowing for both an axial and azimuthal variation of the conductor currents. It is shown that for the bare buried conductor case, the accurate determination of the propagation constant is imperative for calculating the fields at the earth's surface. Further, it is shown that the thin-wire approximation is not valid for determining the fields in both the far and near field regions when the conductor is buried in close proximity to the interface. These results imply that the use of the thin-wire approximation and the uniform axial current assumption may not be valid for commonly occurring buried conductor problems.