Spherical ADI FDTD Method With Application to Propagation in the Earth Ionosphere Cavity

• Published in: IEEE transactions on antennas and propagation Vol. 60; no. 1; pp. 310 - 317
• Main Authors: Paul, D. L., Railton, C. J.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.01.2012; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Alternating direction implicit (ADI) finite-difference time-domain (FDTD); Applied classical electromagnetism; Earth; Earth ionosphere cavity; Electromagnetic wave propagation, radiowave propagation; Electromagnetism; electron and ion optics; Equations; Exact sciences and technology; extremely low frequencies (ELF) propagation; Finite difference methods; Fundamental areas of phenomenology (including applications); Ionosphere; Meteorology; Physics; Schumann resonances; spherical FDTD; Studies; Three dimensional displays; Time domain analysis; Alternating direction method; Transient response; Implicit method; Schumann resonances; Finite difference time-domain analysis; Lossy medium; Numerical method; Coordinate system; Time response; Implementation; Alternating direction implicit (ADI) finite-difference time-domain (FDTD); Cavities; Computation time; spherical FDTD; Three dimensional model; Accuracy; Wave propagation; Earth ionosphere cavity; Spherical coordinate; Extremely low frequency; Computational electromagnetics; Ionosphere; extremely low frequencies (ELF) propagation
• ISSN: 0018-926X; 1558-2221
• DOI: 10.1109/TAP.2011.2167940

The alternating direction implicit (ADI) finite-difference time-domain (FDTD) technique is implemented using the spherical coordinate system and applied to wave propagation in the lossy Earth ionosphere cavity. The paper shows, for the first time, that the ADI technique can be developed in conjunction with spherical FDTD in order to overcome the typically long computing times involved in Earth ionosphere cavity problems. Numerical accuracy of the full wave three-dimensional (3D) ADI implementation is validated by comparison with spherical FDTD results. While not free from late time instability, transient responses are shown to be obtained accurately for time steps as large as 15 times the time step derived from cells at the Equator. Hence the spherical ADI is demonstrated to be a promising technique to efficiently characterize Schumann resonances and other complex propagation phenomena around the Earth, while overcoming the space cell eccentricity typically generated by spherical grids.