A review of progress in FDTD Maxwell's equations modeling of impulsive subionospheric propagation below 300 kHz

pre-printWave propagation at the bottom of the electromagnetic spectrum (below300 kHz) in the Earth-ionosphere waveguide system has been an interesting and important area of investigation for the last four decades. Such wave propagation is characterized by complex phenomena involving nonhomogeneous and anisotropic media, and can result in resonances of the entire Earth-ionosphere cavity. In the spirit of this Special Issue, the goal of this paper is to call attention to emerging finite-difference time-domain computational solutions of Maxwell's equations for wave propagation below 300 kHz which promise to complement and extend previous analyses by pioneers such as Profs. Wait and Felsen. The following topical areas are discussed: long-range two-dimensional propagation, lightning sources and radiation, global propagation, Schumann resonances, hypothesized pre-seismic lithosphere sources and radiation, detection of deep underground resource formations, and remote sensing of localized ionospheric anomalies. We conclude with a prospectus for future research, especially in incorporating the physics of the anisotropic, nonhomogeneous magnetized plasma in a global planetary ionosphere

Current and future applications of 3-D global earth-ionosphere waveguide models based on the full-vector maxwells equations FDTD method

pre-printAdvances in computing technologies in recent decades have provided a means of generating and performing highly sophisticated computational simulations of electromagnetic phenomena. In particular, just after the turn of the 21st century, improvements to computing infrastructures provided for the first time the opportunity to conduct advanced, high-resolution three-dimensional full-vector Maxwell's equations investigations of electromagnetic propagation throughout the global Earth-ionosphere spherical volume. In particular, global models employing the finite-difference time-domain (FDTD) method are capable of including such details as the Earth's topography and bathymetry, as well as arbitrary horizontal / vertical geometrical and electrical inhomogeneities and anisotropies of the ionosphere, lithosphere, and oceans. Studies at this level of detail simply are not achievable using analytical methods. The goal of this Paper is to provide an historical overview and future prospectus of global FDTD computational research for both natural and man-made electromagnetic phenomena around the world. Current and future applications of global FDTD models relating to lightning sources and radiation, Schumann resonances, hypothesized earthquake precursors, remote sensing, and space weather are discussed

Three-dimensional FDTD modeling of impulsive ELF propagation about the earth-sphere

pre-printThis paper reports the application of an efficient finite-difference time-domain (FDTD) algorithm to model impulsive extremely low frequency (ELF) propagation within the entire Earth-ionosphere cavity. Periodic boundary conditions are used in conjunction with a three-dimensional latitude-longitude FDTD space lattice which wraps around the complete Earth-sphere. Adaptive combination of adjacent grid cells in the east-west direction minimizes cell eccentricity upon approaching the poles and hence maintains Courant stability for relatively large time steps. This technique permits a direct, three-dimensional time-domain calculation of impulsive, round-the-world ELF propagation accounting for arbitrary horizontal as well as vertical geometrical and electrical inhomogeneities/anisotropies of the excitation, ionosphere, lithosphere, and oceans. The numerical model is verified by comparing its results for ELF propagation attenuation with corresponding data reported in the literature

An E-J collocated 3-D FDTD model of electromagnetic wave propagation in magnetized cold plasma

pre-printA new three-dimensional finite-difference time-domain (FDTD) numerical model is proposed herein to simulate electromagnetic wave propagation in an anisotropic magnetized cold plasma medium. Plasma effects contributed by electrons, positive, and negative ions are considered in this model. The current density vectors are collocated at the positions of the electric field vectors, and the complete FDTD algorithm consists of three regular updating equations for the magnetic field intensity components, as well as 12 tightly coupled differential equations for updating the electric field components and current densities. This model has the capability to simulate wave behavior in magnetized cold plasma for an applied magnetic field with arbitrary direction and magnitude. We validate the FDTD algorithm by calculating Faraday rotation of a linearly polarized plane wave. Additional numerical examples of electromagnetic wave propagation in plasma are also provided, all of which demonstrate very good agreement with plasma theory

Doctor of Philosophy

dissertatio

Derivation of a Closed-Form Approximate Expression for the Self-Capacitance of a Printed Circuit Board Trace

The electric fields that couple traces on printed circuit boards to attached cables can generate common-mode currents that result in significant radiated emissions. Previous work has shown that these radiated emissions can be estimated based on the self-capacitances of the microstrip structures on a board . In general, the determination of these self-capacitances must be done numerically using three-dimensional static modeling software. In this paper, an approximate closed-form expression for the self-capacitance of microstrip traces is derived. This expression can be used to estimate the voltage-driven common-mode emissions from boards with various microstrip trace geometries. The expression also provides insight relative to the microstrip parameters that have the greatest effect on radiated emissions

Modelling of VLF radio propagation in the earth-ionosphere waveguide.

M. Sc. University of KwaZulu-Natal, Durban 2012.Abstract available in PDF file

A geodesic finite-difference time-domain model of magnetized plasma

Electromagnetic wave propagation in the Earth-ionosphere cavity presents an interesting challenge for simulations. Three-dimensional latitude-longitude finite-difference time-domain (FDTD) models accounting for the bathymetry, topography and ionosphere have been developed and applied towards a number of applications previously. However, to date most of these models treat the ionosphere as a simple, isotropic exponential conductivity profile. Only recently has a latitude-longitude FDTD model been developed that treats the ionosphere as a magnetized cold plasma. This opens the door to modeling electromagnetic phenomena at higher frequencies and higher altitudes by accommodating more physics. Further, a geodesic (hexagonal-pentagonal) FDTD model that is more efficient, is easier to implement, and executes faster than latitude-longitude models has been recently developed. In this thesis, the magnetized cold plasma global latitude-longitude algorithm is adapted and implemented for the first time in a geodesic FDTD model of the Earth-ionosphere cavity