ON THE USE OF ELECTROMAGNETIC WAVES IN GEOPHYSICAL PROSPECTING

Geophysics ◽  
1946 ◽  
Vol 11 (4) ◽  
pp. 505-517 ◽  
Author(s):  
C. W. Horton
Keyword(s):  
Thin Layer ◽  
Electromagnetic Waves ◽  
Salt Water ◽  
Step Function ◽  
Approximate Analysis ◽  
Geophysical Prospecting ◽  
First Order ◽  
The Earth ◽  
Displacement Currents ◽  
Geological Formations

An approximate analysis of the behavior of electromagnetic waves in a conducting medium is given. The approximations consist of replacing pairs of electrodes by dipoles and of using only the first order images in the case of a layered earth. It is shown that under typical conditions one can measure the depth of an electrical interface 6,000 feet deep by means of electromagnetic waves. It is further shown that even a thin layer of salt water or oil bearing sand at a depth of 6,000 feet gives an effect that is easily measureable. The response of the earth to a d.c. step function is analysed for the case in which the displacement currents are negligible. This approximation is valid for all geological formations. The shape of a commutated direct current is shown as a function of the distance of travel.

scholarly journals Thin Layer Models for Electromagnetism

2014 ◽  
Vol 16 (1) ◽  
pp. 213-238 ◽  
Author(s):  
Marc Duruflé ◽  
Victor Péron ◽  
Clair Poignard
Keyword(s):  
Electromagnetic Field ◽  
Thin Layer ◽  
Electromagnetic Waves ◽  
Scattering Problem ◽  
Specific Behavior ◽  
Low Frequencies ◽  
First Order ◽  
Asymptotic Models ◽  
Multiscale Expansion ◽  
Electrical Conductivities

AbstractWe present a review on the accuracy of asymptotic models for the scattering problem of electromagnetic waves in domains with thin layer. These models appear as first order approximations of the electromagnetic field. They are obtained thanks to a multiscale expansion of the exact solution with respect to the thickness of the thin layer, that makes possible to replace the thin layer by approximate conditions. We present the advantages and the drawbacks of several approximations together with numerical validations and simulations. The main motivation of this work concerns the computation of electromagnetic field in biological cells. The main difficulty to compute the local electric field lies in the thinness of the membrane and in the high contrast between the electrical conductivities of the cytoplasm and of the membrane, which provides a specific behavior of the electromagnetic field at low frequencies.

Seti Space Missions

1997 ◽  
Vol 161 ◽  
pp. 761-776 ◽  
Author(s):  
Claudio Maccone
Keyword(s):  
Electromagnetic Waves ◽  
Space Missions ◽  
Gravitational Lens ◽  
The Sun ◽  
Space Antenna ◽  
Focal Distance ◽  
Large Space ◽  
The Earth ◽  
Space Antennas ◽  
New Space

AbstractSETI from space is currently envisaged in three ways: i) by large space antennas orbiting the Earth that could be used for both VLBI and SETI (VSOP and RadioAstron missions), ii) by a radiotelescope inside the Saha far side Moon crater and an Earth-link antenna on the Mare Smythii near side plain. Such SETIMOON mission would require no astronaut work since a Tether, deployed in Moon orbit until the two antennas landed softly, would also be the cable connecting them. Alternatively, a data relay satellite orbiting the Earth-Moon Lagrangian pointL2would avoid the Earthlink antenna, iii) by a large space antenna put at the foci of the Sun gravitational lens: 1) for electromagnetic waves, the minimal focal distance is 550 Astronomical Units (AU) or 14 times beyond Pluto. One could use the huge radio magnifications of sources aligned to the Sun and spacecraft; 2) for gravitational waves and neutrinos, the focus lies between 22.45 and 29.59 AU (Uranus and Neptune orbits), with a flight time of less than 30 years. Two new space missions, of SETI interest if ET’s use neutrinos for communications, are proposed.

ELECTRIC EARTH TRANSIENTS IN GEOPHYSICAL PROSPECTING

Geophysics ◽  
1936 ◽  
Vol 1 (2) ◽  
pp. 271-277 ◽  
Author(s):  
Louis Statham
Keyword(s):  
Electric Current ◽  
Salt Dome ◽  
Geophysical Prospecting ◽  
The Earth ◽  
Electrical Methods ◽  
The Times

A suddenly applied electric current is passed through the earth by means of spaced electrodes. The form of the potential transient as it appears outside the current electrodes is studied. The potential transient is extremely rapid and refined methods of recording are necessary. Means for measuring the relative times of the transient potentials received from different points are discussed. A survey taken over a known deep salt dome is shown; anomalous times of the transients are found to exist over the dome. No correlation is seen between the times of the transients and the resistivity as found by ordinary electrical methods.

On modeling a well casing for resistivity and induced polarization

Geophysics ◽  
1984 ◽  
Vol 49 (11) ◽  
pp. 2061-2063 ◽  
Author(s):  
James R. Wait
Keyword(s):  
Electrical Properties ◽  
Electric Dipole ◽  
Free Space ◽  
Eddy Currents ◽  
Interfacial Polarization ◽  
Induced Polarization ◽  
Mutual Impedance ◽  
The Earth ◽  
Horizontal Electric Dipole ◽  
Displacement Currents

In a previous communication I proposed an analytical model to simulate the electromagnetic (EM) and induced polarization (IP) response of a metal well casing (Wait, 1983). To facilitate the analysis, the earth was idealized as a homogeneous conducting half‐space of electrical properties (σ, ε, μ). The well casing was represented as a filamental vertical conductor of semiinfinite length that was characterized by a series axial impedance to account for eddy currents and interfacial polarization. A further basic simplification was to neglect displacement currents in the air; this was justified when all significant distances were small compared with the free‐space wavelength. Initially, the source was taken to be a horizontal electric dipole or current element I ds on the air‐earth interface. By integration of the results, the mutual impedance between two grounded circuits could be ascertained. In the absence of the vertical conductor (i.e., the well casing) the results reduced to those given by Sunde (1968) and Ward (1967).

scholarly journals SMT-Based System Verification with DVF

10.29007/59rn ◽  
2018 ◽  
Author(s):  
Amit Goel ◽  
Sava Krstic ◽  
Rebekah Leslie ◽  
Mark Tuttle
Keyword(s):  
Thin Layer ◽  
Type System ◽  
Transition Systems ◽  
First Order ◽  
Verification Conditions ◽  
Logic Verification ◽  
System Verification ◽  
Selected Subset ◽  
Parametric Specification

We introduce the <i>Deductive Verificaton Framework</i> (DVF), a language and a tool for verifying properties of transition systems. The language is procedural and the system transitions are a selected subset of procedures. The type system and built-in operations are consistent with SMT-LIB, as are the multisorted first-order logical formulas that may occur in DVF programs as pre- and post-conditions, assumptions, assertions, and goals. A template mechanism allows parametric specification of complex types within the confines of this logic. Verification conditions are generated from specified goals and passed to SMT engine(s). A general assume-guarantee scheme supports a thin layer of interactive proving.

Corrosion Margins for Redundant Ship Structures

2018 ◽  
Author(s):  
Yordan Garbatov ◽  
C. Guedes Soares
Keyword(s):  
Differential Equation ◽  
Degradation Process ◽  
Step Function ◽  
Order System ◽  
Safety Factors ◽  
Ship Structures ◽  
Degradation Model ◽  
Corrosion Depth ◽  
First Order ◽  
Partial Safety Factors

The work presented here analyses the structural corrosion degradation of two sets of corrosion depth measurements collected with a one-decade difference. The corrosion degradation process is associated to a first order system, subjected to a sudden disturbance, where a step function is used as an input to define the solution of the differential equation of this system leads to the exponential corrosion degradation model as developed earlier. Corrosion margins of redundant ship structures with serious consequences of failure are derived and several conclusions related to the new trend in the ageing structures are presented and discussed. Partial safety factors with respect to the corrosion environment and corrosion margins are developed that can be used in the design, avoiding a complex probabilistic analysis.

The strength of the Earth’s magnetic field from Pre-Pottery to Pottery Neolithic, Jordan

2021 ◽  
Author(s):  
Anita Di Chiara ◽  
Lisa Tauxe ◽  
Thomas Levy ◽  
Mohammand Najjar ◽  
Fabio Florindo ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Dipole Moments ◽  
Ancient Egypt ◽  
Archaeological Sites ◽  
Southern Levant ◽  
Short Term ◽  
The Past ◽  
The Earth ◽  
Secular Variations ◽  
Geological Formations

<p>Constraining the secular variations of the Earth’s magnetic field strength in the past is fundamental to understanding short term processes of the geodynamo. Such records constitute a powerful and independent dating tool for archaeological sites and geological formations. In this study, we present 10 new and robust archaeointensity results from Pre-Pottery to Pottery Neolithic and, for one of the first times, flint (burnt chert) from Jordan. Two of these results constitute the oldest archaeointensity data for the entire Levant, ancient Egypt and Mesopotamia extending the archaeomagnetic dating reference for the Holocene. Virtual Axial Dipole Moments (VADM)s show that the Earth’s magnetic field in the Southern Levant was weak (about half the present field) at around 7,600 years BCE, recovering its strength to greater than the present field around 7,100 BCE and gradually weakening again around 5,200 years BCE. In addition, successful results obtained from burnt flint demonstrate the potential of this rarely used material in archaeomagnetic research, in particular for prehistoric periods from the first use of fire to the invention of pottery.</p>

scholarly journals Tidal Variations of the Earth Rotation

2000 ◽  
Vol 178 ◽  
pp. 565-569
Author(s):  
J.M. Ferrándiz ◽  
Yu. V. Barkin ◽  
J. Getino
Keyword(s):  
Angular Velocity ◽  
Earth Rotation ◽  
Polar Motion ◽  
Deformable Body ◽  
The Moon ◽  
First Order ◽  
Andoyer Variables ◽  
The Earth ◽  
Tidal Deformations ◽  
Tidal Variations

AbstractThe equations for the rotation of a weakly deformable celestial body in non canonical Andoyer variables have been used to study the perturbation of Earth rotation due to tidal deformation raised by the Moon and Sun. A theory of the perturbed rotational motion of an isolated weakly deformable body in Andoyer variables and in components of the angular velocity has been developed. Mantle tidal deformations due to lunar and solar influences were analytically described and taken into account. Perturbations of the first order in the Earth’s polar motion were determined.

scholarly journals Model of the propagation of very low-frequency beams in the Earth–ionosphere waveguide: principles of the tensor impedance method in multi-layered gyrotropic waveguides

2020 ◽  
Vol 38 (1) ◽  
pp. 207-230
Author(s):  
Yuriy Rapoport ◽  
Vladimir Grimalsky ◽  
Viktor Fedun ◽  
Oleksiy Agapitov ◽  
John Bonnell ◽  
...  
Keyword(s):  
Optical Waveguides ◽  
Electromagnetic Waves ◽  
Low Frequency ◽  
Signal Propagation ◽  
Wide Frequency Range ◽  
Impedance Method ◽  
Very Low Frequency ◽  
The Earth ◽  
Tensor Impedance ◽  
Electromagnetic Beams

Abstract. The modeling of very low-frequency (VLF) electromagnetic (EM) beam propagation in the Earth–ionosphere waveguide (WGEI) is considered. A new tensor impedance method for modeling the propagation of electromagnetic beams in a multi-layered and inhomogeneous waveguide is presented. The waveguide is assumed to possess the gyrotropy and inhomogeneity with a thick cover layer placed above the waveguide. The influence of geomagnetic field inclination and carrier beam frequency on the characteristics of the polarization transformation in the Earth–ionosphere waveguide is determined. The new method for modeling the propagation of electromagnetic beams allows us to study the (i) propagation of the very low-frequency modes in the Earth–ionosphere waveguide and, in perspective, their excitation by the typical Earth–ionosphere waveguide sources, such as radio wave transmitters and lightning discharges, and (ii) leakage of Earth–ionosphere waveguide waves into the upper ionosphere and magnetosphere. The proposed approach can be applied to the variety of problems related to the analysis of the propagation of electromagnetic waves in layered gyrotropic and anisotropic active media in a wide frequency range, e.g., from the Earth–ionosphere waveguide to the optical waveband, for artificial signal propagation such as metamaterial microwave or optical waveguides.

Sign in / Sign up

Export Citation Format

Share Document