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.