The propagation model and characteristics for extremely low frequency electromagnetic wave in Earth-ionosphere system and its application in geophysics prospecting

Qu, Xiaodong; Xue, Bing; Fang, Guangyou

doi:10.1080/09205071.2017.1383194

Cited by 3 publications

(4 citation statements)

References 16 publications

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“…As was the case for Figure 7b,d, the interpretation of Figure 8b,d will be analyzed in detail below. Figure 8 indicates that the electric fields significantly attenuate near the height of 60 km, which is influenced by the inflection point of the conductivity knee model and is coherent with the simulation results of [42]. S. The EM wave firstly appears near a longitude of 176 • E at 0.02 s and then diffuses and propagates towards the west and east, as shown in Figure 9.…”

Section: Casesupporting

confidence: 79%

“…Ref. [42] simulated the Earth-ionosphere system model utilizing a three-dimensional FDTD algorithm and Maxwell equations on the neutral medium, whose excitation sources are Gaussian pulse current sources on the Earth's surface. They analyzed the distribution of ELF EM fields in a local area and their simulation results of the propagation process in atmosphere and ionosphere were consistent with ours.…”

Section: Discussionmentioning

confidence: 99%

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Numerical Study of Global ELF Electromagnetic Wave Propagation with Respect to Lithosphere–Atmosphere–Ionosphere Coupling

et al. 2021

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Before and after earthquakes, abnormal physical and chemical phenomena can be observed by gathering ground-based and satellite data and interpreted by the lithosphere–atmosphere–ionosphere coupling (LAIC) mechanism. In this study, we focused on the mechanism of LAIC electromagnetic radiation and investigated the seismic electromagnetic (EM) wave generated in the lithosphere by earthquakes and its global propagation process from the lithosphere through the atmosphere and into the bottom of ionosphere, in order to analyze the abnormal disturbance of ground-based and space-based observation results. First, analytic formulas of the electrokinetic effect were used to simulate the generation and propagation process of the seismic EM wave in the lithosphere, interpreted as the conversion process of the seismic wave and EM wave in porous media. Second, we constructed a three-dimensional Earth–ionosphere waveguide by applying the finite-difference time-domain (FDTD) algorithm to model the global propagation process of the seismic EM wave into the atmosphere and cavity between the bottom of the ionosphere and the surface of the Earth. By combining the model of the electrokinetic effect in the lithosphere with the numerical model of the Earth–ionosphere waveguide in the atmosphere and ionosphere, we numerically simulated the global transmission process of extremely low-frequency (ELF: 3 Hz–3000 Hz) EM waves which are related to earthquakes. The propagation parameters of coseismic ELF EM waves with different duration times and center frequencies were analyzed and summarized. The simulation results demonstrate that the distribution characteristics of an electric field along longitude, latitude and altitude with time are periodic and the time interval during which an EM wave travels around the whole Earth is approximately 0.155 s when adopting the conductivity of the knee profile. We also compared the observation data with the simulation results and found that the attenuating trends of the ELF electric field are consistent. This proposed ELF EM wave propagation model of lithosphere–atmosphere–ionosphere coupling is very promising for the explanation of abnormal disturbances of ground-based and space-based observation results of ELF EM fields which are associated with earthquakes.

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Section: Casesupporting

confidence: 79%

Section: Discussionmentioning

confidence: 99%

Numerical Study of Global ELF Electromagnetic Wave Propagation with Respect to Lithosphere–Atmosphere–Ionosphere Coupling

et al. 2021

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“…There are two methods to solve this problem: the first one is assuming that atmospheric and Earth layers are relatively flat; the other is to consider the spherical atmosphere and the Earth, and thus obtain a spherical harmonics series solution in a spherical coordinate system [10]. Since the pioneering works of J. R. Wait [11], J. Galejs [12], Bannister [13], J. P. Casey [14], and Pan and Li [15], many theoretical studies on ELF electromagnetic waves have been performed for different fields, such as communication [14,16], earthquake monitoring [17][18][19], geophysical exploration [20][21][22][23][24], and so on. It is clear that the ELF-EM method is an effective tool for probing the deep underground in a variety of geologic settings [20].…”

Section: Introductionmentioning

confidence: 99%

“…However, the further applications of ELF in deep resources exploration have not been reported. In addition, in previous studies, the Earth was assumed to be a near-perfect conductor or a homogeneous medium [26,27], and the finite-difference time-domain (FDTD) method was used to model the propagation of ELF electromagnetic waves around the Earth sphere [22,28,29], which could not fully reflect the response of the stratified Earth media to a certain extent. Therefore, these models are inadequate for geophysical exploration with the heterogeneity of the interior of the Earth as the main target of interest [30].…”

Section: Introductionmentioning

confidence: 99%

A Spherical “Earth–Ionosphere” Model for Deep Resource Exploration Using Artificial ELF-EM Field

Zheng

2022

Remote Sensing

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Fully coupled lithosphere, atmosphere, and ionosphere theory has demonstrated that extremely low-frequency electromagnetic (ELF-EM) fields present a broad application prospect in deep resource exploration, but previous studies have ignored the contribution of the Earth’s curvature. This study extends the theory of ELF-EM over a stratified Earth to the case where the Earth’s curvature must be taken into account, and presents an analytical solution of the ELF-EM field excited by a grounded horizontal antenna in a spherical Earth–ionosphere model, whose theoretical approach and solution method are notably different from the flat Earth–ionosphere model. Additionally, the Earth is treated as a concentric-layered sphere rather than an ideal homogeneous sphere. We aim to investigate the effects of the Earth’s curvature on the surface field, so as to broaden the coverage of the ELF wave in resource exploration. The solution is mathematically accurate and physically reasonable, since it reflects the sphericity and radially stratified structure of the Earth. We first verify the correctness and reliability of the proposed method by comparing the results with FDTD in a full-space spherical model. Additionally, we then compared the spherical results with the conventional controlled-source electromagnetic method and flat Earth–ionosphere results. The results show that when the distance between the transmitter and the receiver is comparable to the Earth radius, the spherical model better reflects the resonance of the wave in the cavity, suggesting that the effect of the Earth’s curvature is not negligible. Then, the numerical simulations conducted to investigate the properties of the EM fields and their sensitivities to the conductivity at depth in the Earth are discussed. Finally, the EM responses of some simple electrical conductivity structures models are modeled to illustrate their prospects in future resource exploration.

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A portable frequency‐domain electromagnetic detection system

Peng,

Zhao,

Zhang

et al. 2024

Circuit Theory & Apps

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SummaryFrequency‐domain detection stands as a critical method in remote geophysical exploration; however, its practical application is constrained by the considerable size of the requisite instrumentation. In this paper, we present a compact frequency domain electromagnetic detection system. The integration of intelligent power devices and a novel hardware architecture substantially diminishes the system's dimensions, thereby enhancing its portability. Furthermore, the system design incorporates sinusoidal pulse width modulation and digital phase‐locked amplification to ensure the efficacy of the proposed system. Both the transmitter and receiver system are constrained to dimensions smaller than 1.5 m. Subsequent experimental validation attests to the exemplary hardware performance of the proposed system, with the transmitting voltage of the transmitter circuit attaining 500 V, and the receiver circuit exhibiting a sensitivity as low as 10−8 V. Significantly, this design paradigm not only facilitates the integration of transmitter and receiver systems for frequency‐domain electromagnetic detection but also introduces novel prospects for the application of frequency‐domain electromagnetic detection methods across diverse fields.

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The propagation model and characteristics for extremely low frequency electromagnetic wave in Earth-ionosphere system and its application in geophysics prospecting

Cited by 3 publications

References 16 publications

Numerical Study of Global ELF Electromagnetic Wave Propagation with Respect to Lithosphere–Atmosphere–Ionosphere Coupling

Numerical Study of Global ELF Electromagnetic Wave Propagation with Respect to Lithosphere–Atmosphere–Ionosphere Coupling

A Spherical “Earth–Ionosphere” Model for Deep Resource Exploration Using Artificial ELF-EM Field

A portable frequency‐domain electromagnetic detection system

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