Scattering of electromagnetic waves by a material half-space with a time-varying conductivity

This paper analyzes for the first time electromagnetic wave penetration and scattering interactions for a material half-space having sinusoidally time-varying conductivity. Two limiting cases are considered. The first assumes that the material conductivity is almost a constant with a small temporal perturbation. The problem is accordingly attacked with first-order perturbation methods. The second exploits a large dimensionless parameter and yields an asymptotic expansion of the field inside a highly conducting material undergoing sinusoidal time variation. Illustrative examples are given which agree well with numerically obtained finite-difference time-domain (FDTD) results.