Theory of Transmission of Electromagnetic Waves along a Drill Rod in Conducting Rock

We present an analysis of the electromagnetic fields excited by a toroidal cofl that is coaxial with a circular metal rod located in a conducting medium. The integral representation for the induced axial current on the rod is cast in a form that is suitable for numerical evaluation. Some results for the electric current distribution on the infinitely long configuration are given for a fixed magnetic current source. Good agreement is obtained with an asymptotic estimate for this quantity. The effects of truncating the bottom end of the rod and terminating the top in an ideal ground plane are treated by an approximate method. Numerical results for this confilguration are also given.