Two-dimensional current diffusion in an EML rail with constant properties

We develop an exact solution to Maxwell's equations to describe the diffusion of the current both along and across an EML rail which satisfies appropriate boundary conditions on all rail surfaces. We argue that assuming a sheath of current uniform along the rail (the 1-D solution) leads to underestimates of the Joule heating near the bore surface, and hence overestimates of the survivability of the bore surface of a rail.