Electromagnetic fields about a flat circular electrode

Although different sources have been studied in geophysics, a rigorous study of tbc role of surface distributed sources of alternating current is virtually missing in the geophysical literature. In fact, sources of electromagnetic radiation defined at surfaces play an important role and can emerge in many practical applications. The goal of this paper is Io solve the problem of electromagnetic radiation generated by an alternating current dipole distributed on a perfeetly condueting thin circular disk, and perpendicular Io it. So tbc importance of fiat electrodes as a source of an electromagnetic field in geophysical exploration can be understood. The problem entaìls a solution of lincar Maxwell's equations in the frequeney domain, using the Hankel transform applied Io modified Helinholtz wave equations. This procedure reduces the wave equations Io a system of ordinary differential equations with respect Io the vertical coordinate. Unknown coefficients are sought from the continuity of boundary values for the field components and jump discontinuitics of their first derivatives at the source location. Different complexities such as underlying multilayered media can be casily compounded Io a solution by increasing the number of equations satisfying the boundary conditions at tbc interfaces. Tbc solution obtaincd allows calculation of both the primary and the scattered electromagnetic field components radiated from disk sources of alternating current situated in a conduetive media. The computed values of the azimuthal component of the magnetic field, and tbc radial component of the electric field show that for distances less than one hundred disk radio the contribution of a Ilat electrode is significant. Because of this and the finite size and geometry of the disk source it is advantageous Io employ it for parametric sounding with a small distanec between transmitter and recciver. For larger distances tbc flat electrode may be adequately employed so that the magnitude of the produced field is much lower than tbc magnitude of the anomaly field induced by the shielded cables.