Finite-difference time-domain solution of Maxwell´s equations for the dispersive ionosphere

The application of the finite-difference time-domain (FDTD) technique to problems in ionospheric radio wave propagation is complicated by the dispersive nature of the ionospheric plasma. In the time domain, the electric displacement is the convolution of the dielectric tensor with the electric field, and thus requires information from the entire signal history. It is shown that this difficulty can be avoided by returning to the dynamical equations from which the dielectric tensor is derived. By integrating these differential equations simultaneously with the Maxwell equations, temporal dispersion is fully incorporated. An FDTD approach utilizing the vector wave equation is also presented. The accuracy of the method is shown by comparison for a special case for which an analytic solution is available. The method is demonstrated with examples of pulse propagation in one and two dimensions. The computational limitations of present-generation computers are discussed. The application of this approach to the study of wave propagation in randomly structured ionization is addressed.<>