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Jean-pierre Bérenger - One of the best experts on this subject based on the ideXlab platform.
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FDTD propagation of VLF-LF waves in the presence of ions in the Earth-Ionosphere waveguide
Annals of Telecommunications, 2020Co-Authors: Jean-pierre BérengerAbstract:The finite-difference time-domain (FDTD) method has been used for a long time to compute the propagation of very low frequency (VLF) and low frequency (LF) radio waves in the Earth-Ionosphere waveguide. In previously published FDTD schemes, only the electronic density of the Ionosphere was accounted for, since in usual natural conditions the effect of the ion density can be neglected. In the present paper, the FDTD scheme is extended to the case where one or several ion species must be accounted for, which may occur in special natural conditions or in such artificial conditions as after high altitude nuclear bursts. The conditions that must hold for the effect of the ions not to be negligible are discussed, the FDTD scheme with ions is derived, and numerical experiments are provided to show that the effect of the ions may be significant when the Ionosphere is disturbed by incident flows of γ or β rays.
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an implicit fdtd scheme for the propagation of vlf lf radio waves in the Earth Ionosphere waveguide
Comptes Rendus Physique, 2014Co-Authors: Jean-pierre BérengerAbstract:A new finite-difference time-domain scheme is presented for the propagation of VLF–LF radio waves in the Earth–Ionosphere waveguide. The new scheme relies on the implicit solution of the auxiliary equation that governs the current density in the Ionosphere. The advantages and drawbacks of the new scheme are discussed. Its main advantage is its stability condition, which is the same as that of the FDTD method in a vacuum. This permits the time step of the calculation to be increased and then the overall computational time to be reduced. Numerical experiments demonstrate the accuracy of the new scheme and the reduction of the computational time.
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REDUCTION OF THE ANGULAR DISPERSION OF THE FDTD METHOD IN THE Earth-Ionosphere WAVEGUIDE
Journal of Electromagnetic Waves and Applications, 2003Co-Authors: Jean-pierre BérengerAbstract:This paper presents a simple technique used to reduce the angular dispersion of the finite-difference time-domain (FDTD) method applied to the propagation of VLF-LF radiowaves in the Earth-Ionosphere waveguiding structure. This technique is based on the introduction of an artificial anisotropy in the Maxwell equations.
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FDTD computation of vlf-lf propagation in the Earth-Ionosphere waveguide
Annales Des Télécommunications, 2002Co-Authors: Jean-pierre BérengerAbstract:This paper describes the application of the finite-difference time-domain method (fdtd) to the calculation of vlf-lf radiowave propagation in the Earth-Ionosphere waveguide. Special techniques have been developed to render the computational time acceptable, namely the use of a moving computational domain and the introduction of an artificial anisotropy in view of reducing the anisotropy of the fdtd scheme. Numerical experiments are provided to illustrate the good agreement of the fdtd method with the waveguide method.RésuméCet article décrit l’application de la méthode des différences finies temporelles au calcul de la propagation des ondes kilométriques et myriamétriques (vlf-lf) dans le guide d’onde Terre-ionosphère. Des techniques particulières sont mises en oeuvre pour rendre le temps de calcul acceptable, à savoir l’utilisation d’un volume de calcul mobile et l’introduction d’une anisotropie artificielle destinée à réduire l’anisotropie du schéma numérique. Des résultats de calcul illustrent le très bon accord de la méthode des différences finies et de la méthode des modes.
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FDTD computation of vlf-lf propagation in the Earth-Ionosphere waveguide
Annales Des Télécommunications, 2002Co-Authors: Jean-pierre BérengerAbstract:This paper describes the application of the finite-difference time-domain method (fdtd) to the calculation of vlf-lf radiowave propagation in the Earth-Ionosphere waveguide. Special techniques have been developed to render the computational time acceptable, namely the use of a moving computational domain and the introduction of an artificial anisotropy in view of reducing the anisotropy of the fdtd scheme. Numerical experiments are provided to illustrate the good agreement of the fdtd method with the waveguide method.
James R. Wait - One of the best experts on this subject based on the ideXlab platform.
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VLF scattering from a column of ionization in the Earth-Ionosphere waveguide
Journal of Atmospheric and Terrestrial Physics, 1995Co-Authors: James R. WaitAbstract:Abstract Choosing a highly idealized model, we analyze the scattering of VLF radio waves from a thin vertical column of ionization within the Earth-Ionosphere waveguide. It is shown that mode conversion is produced if the column is limited in height and/or if the ionization is a function of height. However, the relative higher-mode content would be small in some situations such as in the case of the ionization produced by a cloud-to-Ionosphere lightning discharge.
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On ELF transmission in the Earth-Ionosphere waveguide
Journal of Atmospheric and Terrestrial Physics, 1992Co-Authors: James R. WaitAbstract:The propagation constant for ELF (extremely low frequency) propagation in the Earth Ionosphere waveguide is determined analytically. The derivation carried out for a planar model, with the Earth's surface impedance Zg> 0, confirms the important result obtained earlier by Greifinger and Greifinger [(1978), Radio Sci. 13, 831] in the limitZg = 0. The present method avoids the use of auxiliary potentials.
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EM scattering from a vertical column of ionization in the Earth-Ionosphere waveguide
IEEE Transactions on Antennas and Propagation, 1991Co-Authors: James R. WaitAbstract:An idealized analysis is given for the mode conversion in the Earth-Ionosphere waveguide produced by a tongue or stalactite of ionization below the normal reflecting layer. It is shown that the scattered signal may be significant even for perturbations located off the great circle path between source and observer. >
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VLF scattering from red sprites: vertical columns of ionisation in the Earth-Ionosphere waveguide
MMET Conference Proceedings. 1998 International Conference on Mathematical Methods in Electromagnetic Theory. MMET 98 (Cat. No.98EX114), 1Co-Authors: Craig J. Rodger, James R. Wait, Neil R. ThomsonAbstract:Optically, red sprites are observed as clusters of short-lived (/spl sim/50 ms) pinkish-red luminous columns, stretching from /spl sim/40 km to /spl sim/85 km altitude, each about 1 km wide. Red sprite discharges produce columns of ionisation in the Earth-Ionosphere waveguide, which can persist for up to /spl sim/100 s at higher altitudes. The ionised columns have been observed through "VLF sprites", perturbations of the phase and/or amplitude of subionospheric VLF transmissions, which can be used to study the electrical properties of the red sprite columns. Previous theoretical studies of red sprite columns have simplified the problem by assuming the columns were of infinite length, or inside a "flat-Earth" waveguide. We present calculations using well-developed VLF propagation methods to describe a finite length sprite inside a realistic Earth-Ionosphere waveguide.
Earle Williams - One of the best experts on this subject based on the ideXlab platform.
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Modeling ELF waves in the non-uniform Earth-Ionosphere cavity
2021Co-Authors: Tamas Bozoki, Erno Pracser, Gabriella Satori, Andrzej Kulak, Janusz Mlynarczyk, Earle WilliamsAbstract:<p>Below 100 Hz, in the lowest part of the extremely low frequency (ELF, 3 Hz - 3 kHz) band lightning-radiated electromagnetic waves propagate with extremely low attenuation (roughly below 1 dB/Mm) within the Earth-Ionosphere waveguide which makes possible the formation of global electromagnetic resonances, known as Schumann resonances (SRs). The most commonly used description of this resonance field assumes a uniform Earth-Ionosphere cavity, i.e. that the propagation conditions for ELF waves are practically the same on the dayside and nightside hemispheres, which is the most vulnerable simplification of these models.&#160;</p><p>In this work we present two different forward models for SRs that take into consideration the day-night asymmetry of the Earth-Ionosphere cavity and are based on the analytical and numerical solutions of the two-dimensional telegraph equation (TDTE). We present numerical tests showing that the two models produce practically the same output, i.e. the relative difference between them is less than 0.4%. The conspicuous conformity between the outputs establishes not only the correctness of the formalisms but the correctness of the implementations (the coding) as well. To the best of the authors&#8217; knowledge this is the first work that verifies this conformity between the two independent solutions.&#160;</p><p>We also compare our stationary models with time-dependent solutions of the TDTE as the stationarity of the resonance field may represent the next most vulnerable simplification that needs to be dismissed to approach a more realistic theoretical description of SRs. All these steps in model development serve our aim to infer global lightning activity based on multi-station ELF measurements by applying a sophisticated inversion algorithm.</p>
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is the Earth Ionosphere capacitor a valid component in the atmospheric global electric circuit
Journal of Atmospheric and Solar-Terrestrial Physics, 2017Co-Authors: C Haldoupis, Earle Williams, Michael J Rycroft, Colin PriceAbstract:Abstract This paper examines whether the Earth-Ionosphere capacitor (EIC) model is correct, by comparing observed atmospheric electrical properties with those expected for a spherical capacitor, as defined in electrostatics. The comparisons suggest that the EIC concept cannot be reconciled with, and hence cannot account for, the observations, particularly the rapid reduction of the atmospheric electric field with height that is measured. This means that the spherical EIC concept is incorrect by being too simplistic; it is thus misleading. The reason for this flawed concept is simple: the model disregards the non-uniform conductivity of the atmosphere which requires the presence of a net positive charge in the lower atmosphere that equals in magnitude the Earth's negative charge. This positive charge shields the action of the Earth's negative charge from polarizing the Ionosphere positively. Thus, the lower D region Ionosphere remains electrically neutral, which makes the EIC concept inappropriate.
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Effects of Energetic Solar Emissions on the Earth–Ionosphere Cavity of Schumann Resonances
Surveys in Geophysics, 2016Co-Authors: Gabriella Satori, Earle Williams, Anirban Guha, Colin Price, Robert Boldi, Alexander Koloskov, Yuri Yampolski, Veronika BartaAbstract:Schumann resonances (SR) are the electromagnetic oscillations of the spherical cavity bounded by the electrically conductive Earth and the conductive but dissipative lower Ionosphere (Schumann in Z Naturforsch A 7:6627–6628, 1952 ). Energetic emissions from the Sun can exert a varied influence on the various parameters of the Earth’s SR: modal frequencies, amplitudes and dissipation parameters. The SR response at multiple receiving stations is considered for two extraordinary solar events from Solar Cycle 23: the Bastille Day event (July 14, 2000) and the Halloween event (October/November 2003). Distinct differences are noted in the ionospheric depths of penetration for X-radiation and solar protons with correspondingly distinct signs of the frequency response. The preferential impact of the protons in the magnetically unshielded polar regions leads to a marked anisotropic frequency response in the two magnetic field components. The general immunity of SR amplitudes to these extreme external perturbations serves to remind us that the amplitude parameter is largely controlled by lightning activity within the Earth–Ionosphere cavity.
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effects of energetic solar emissions on the Earth Ionosphere cavity of schumann resonances
Surveys in Geophysics, 2016Co-Authors: G Satori, Earle Williams, Anirban Guha, Colin Price, Robert Boldi, Alexander Koloskov, Yuri Yampolski, Veronika BartaAbstract:Schumann resonances (SR) are the electromagnetic oscillations of the spherical cavity bounded by the electrically conductive Earth and the conductive but dissipative lower Ionosphere (Schumann in Z Naturforsch A 7:6627–6628, 1952). Energetic emissions from the Sun can exert a varied influence on the various parameters of the Earth’s SR: modal frequencies, amplitudes and dissipation parameters. The SR response at multiple receiving stations is considered for two extraordinary solar events from Solar Cycle 23: the Bastille Day event (July 14, 2000) and the Halloween event (October/November 2003). Distinct differences are noted in the ionospheric depths of penetration for X-radiation and solar protons with correspondingly distinct signs of the frequency response. The preferential impact of the protons in the magnetically unshielded polar regions leads to a marked anisotropic frequency response in the two magnetic field components. The general immunity of SR amplitudes to these extreme external perturbations serves to remind us that the amplitude parameter is largely controlled by lightning activity within the Earth–Ionosphere cavity.
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an improved lorentzian technique for evaluating resonance characteristics of the Earth Ionosphere cavity
Atmospheric Research, 2009Co-Authors: V C Mushtak, Earle WilliamsAbstract:Abstract The effectiveness of various formulations of the Lorentzian procedure for estimating Schumann resonance (SR) characteristics of the Earth-Ionosphere waveguide from transient electromagnetic signals is tested in the limits of a simplified, spherically uniform model of the resonator. It is shown that the major improvement, in comparison with the “classic” Lorentzian formulation, is achieved by consideration of the intra-modal phase interference. The effect of the “limited frequency dispersion” inherent in the “classic” Lorentzian approach – that is of substantial importance at the lowest SR modes – can be effectively neutralized by interpolating the values for the propagation parameter between the adjacent modal frequencies. Several practical aspects of applying the Lorentzian procedure to transient signals are also discussed.
C J Fourie - One of the best experts on this subject based on the ideXlab platform.
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3 d modeling of electromagnetic wave propagation in the uniform Earth Ionosphere cavity using a commercial fdtd software package
IEEE Transactions on Antennas and Propagation, 2017Co-Authors: Christian Kwisanga, C J FourieAbstract:Extremely low frequency (3–3000 Hz) electromagnetic (EM) wave propagation in the (3-D) cavity composed of the Earth’s crust and uniform ionospheric lossy layers is modeled using the finite-difference time-domain algorithm set in a commercial simulation software. EM propagation and attenuation in the Earth-Ionosphere waveguide are computed, and the Schumann resonance (SR) parameters are obtained from the spectra. The overall accuracy of the SR parameters surpasses 90%, despite a fairly coarse resolution of the system. We show that a commercial software can accurately and efficiently model such a large and complex geophysical system.
Weiyan Pan - One of the best experts on this subject based on the ideXlab platform.
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excitation and propagation of slf elf electromagnetic waves in the Earth Ionosphere waveguide cavity
2014Co-Authors: Weiyan PanAbstract:In Chap. 2, the region of interest is a waveguide or cavity between the Earth’s surface and an isotropic homogeneous Ionosphere. Both the dipole source and the observation point are assumed to be located on or near the spherical surface of the Earth. The approximated formulas are obtained for the electromagnetic field radiated by a vertical electric dipole and vertical magnetic dipole in the Earth-Ionosphere waveguide or cavity. Based on the above results, the approximate formulas are derived readily for the electromagnetic field of a horizontal electric dipole in the Earth-Ionosphere waveguide or cavity by using a reciprocity theorem. It is noted that the new approximated algorithm was addressed specially for the whole ELF range as well as the lower end of SLF range (below 50 Hz).
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Spherical Harmonic Series Solution for SLF/ELF Field in the Earth–Ionosphere Waveguide/Cavity
Advanced Topics in Science and Technology in China, 2013Co-Authors: Weiyan PanAbstract:In Chap. 3, the spherical harmonic series solutions are obtained for the SLF/ELF electromagnetic fields of vertical and horizontal electric dipoles in the non-ideal Earth-Ionosphere waveguide or cavity. Especially, the speeding numerical convergence algorithm is used to improve the convergence speed for the spherical harmonic series solutions. It is noted that the SLF/ELF electromagnetic field components in the Earth-Ionosphere waveguide or cavity can be evaluated rapidly with high efficiency by the using this algorithm.
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Excitation and Propagation of SLF/ELF Electromagnetic Waves in the Earth–Ionosphere Waveguide/Cavity
Advanced Topics in Science and Technology in China, 2013Co-Authors: Weiyan PanAbstract:In Chap. 2, the region of interest is a waveguide or cavity between the Earth’s surface and an isotropic homogeneous Ionosphere. Both the dipole source and the observation point are assumed to be located on or near the spherical surface of the Earth. The approximated formulas are obtained for the electromagnetic field radiated by a vertical electric dipole and vertical magnetic dipole in the Earth-Ionosphere waveguide or cavity. Based on the above results, the approximate formulas are derived readily for the electromagnetic field of a horizontal electric dipole in the Earth-Ionosphere waveguide or cavity by using a reciprocity theorem. It is noted that the new approximated algorithm was addressed specially for the whole ELF range as well as the lower end of SLF range (below 50 Hz).
