SIMULATION OF ELECTROMAGNETIC DIFFUSION IN ANISOTROPIC MEDIA

I present an algorithm to simulate low-frequency electro- magnetic propagation in an anisotropic earth, described by a general (non-diagonal) conductivity tensor. I solve the electric formulation by explicitly imposing an approximate form of the condition r ¢ J = 0, where J is the current density vector, which includes the source and the induced current. The numerical algorithm consists of a fully spec- tral explicit scheme for solving linear, periodic parabolic equations. It is based on a Chebyshev expansion of the evolution operator and the Fourier and Chebyshev pseudospectral methods to compute the spatial derivatives. The latter is used to implement the air/ocean boundary conditions. The results of the simulations are verifled by comparison to analytical solutions obtained from the Green function. Examples of the electromagnetic fleld generated by a source located at the bottom of the ocean illustrate the practical uses of the algorithm.