THE EFFECT OF A DIPPING CONTACT ON THE BEHAVIOR OF THE ELECTROMAGNETIC FIELD

Geophysics ◽  
1972 ◽  
Vol 37 (2) ◽  
pp. 337-350 ◽  
Author(s):  
Richard G. Geyer
Keyword(s):  
Magnetic Field ◽  
Plane Waves ◽  
Skin Depth ◽  
Electromagnetic Response ◽  
Vertical Magnetic Field ◽  
Field Phase ◽  
Incident Plane ◽  
Electric And Magnetic Fields ◽  
Orthogonal Components ◽  
Integral Solutions

Theoretical solutions for the electromagnetic response of a dipping interface in the field of normally incident plane waves are given in the form of inverse Lebedev‐Kontorovich transforms. When the lateral resistivity contrast becomes very large, the resulting integral solutions simplify considerably and allow ready numerical evaluation. The amplitude response of the vertical magnetic field seems most diagnostic of the structural attitude of sloping interfaces, even though the vertical magnetic field phase appears relatively insensitive to dip changes compared to horizontal electric field phase. The disturbance in the homogeneity of the field caused by the presence of an inclined contact is postulated to be due to cylindrically diffused waves generated by the dipping interface and propagating along the earth’s surface. It would then seem that formulation of plane‐wave impedances from orthogonal components of the surface electric and magnetic fields would only be applicable at distances from the interface which are large relative to a skin depth in either layer. The results presented here should prove to be useful in detecting and defining sloping interfaces or in avoiding their effects.

THE ELECTRIC AND MAGNETIC FIELDS IN A STRATIFIED FLAT CONDUCTOR FOR INCIDENT PLANE WAVES

1965 ◽  
Vol 43 (5) ◽  
pp. 898-909 ◽  
Author(s):  
H. W. Dosso
Keyword(s):  
Magnetic Fields ◽  
Plane Waves ◽  
Incident Plane ◽  
Electric And Magnetic Fields

The electric and magnetic fields in the upper layer of a stratified flat conductor in the field of plane waves are studied. Expressions for the amplitude and phase of the components of the electric and magnetic fields are obtained and evaluated for various frequencies, angles of incidence, layer thicknesses, depths, and conductivities. The conductivities σ = 10−11 to 10−16 e.m.u. and the frequencies ƒ = 10−3 to 104 cycles/second considered are of interest in geophysics.

scholarly journals The oblique reflexion of very long wireless waves from the ionosphere

1947 ◽  
Vol 189 (1016) ◽  
pp. 130-147 ◽  
Keyword(s):  
Magnetic Field ◽  
Experimental Data ◽  
Theoretical Basis ◽  
Plane Waves ◽  
Angle Of Incidence ◽  
Vertical Magnetic Field ◽  
Radio Waves ◽  
Contour Integrals ◽  
General Terms ◽  
Made In

An attempt is made in the paper to provide a satisfactory theoretical basis for a future discussion of the experimental data on the propagation of very long radio waves (18,800 m.) given by Best, Ratcliffe & Wilkes, and Budden, Ratcliffe & Wilkes. The reflexion of very long plane waves incident obliquely on a horizontally stratified ionized medium with a vertical magnetic field is first considered in general terms, and it is shown that the medium can be divided into a transition region and a reflecting region. If the ionization in the reflecting region increases linearly with height it is shown that propagation is governed by the following equations: ∂ 2 L / ∂ζ 2 + (α + ζ) L + β M = 0, ∂ 2 M / ∂ζ 2 + (α - ζ) M + β L = 0, where α and β are constants depending on the angle of incidence. Under the conditions of the experiments β is small, and a solution, in terms of contour integrals, valid in this case is obtained.

ELECTROMAGNETIC SCATTERING BY CONDUCTORS IN THE EARTH NEAR A LINE SOURCE OF CURRENT

Geophysics ◽  
1971 ◽  
Vol 36 (1) ◽  
pp. 101-131 ◽  
Author(s):  
Gerald W. Hohmann
Keyword(s):  
Magnetic Field ◽  
Half Space ◽  
Line Source ◽  
Numerical Technique ◽  
The Body ◽  
Scale Model ◽  
Electromagnetic Response ◽  
Field Phase ◽  
Horizontal Magnetic Field ◽  
Depth Of Burial

A theoretical solution is developed for the electromagnetic response of a two‐dimensional inhomogeneity in a conductive half‐space, in the field of a line source of current. The solution is in the form of an integral equation, which is reduced to a matrix equation, and solved numerically for the electric field in the body. The electric and magnetic fields at the surface of the half‐space are found by integrating the half‐space Green’s functions over the scattering currents. One advantage of this particular numerical technique is that it is necessary to solve for scattering currents only in the conductor and not throughout the half‐space. The response of a thin, vertical conductor is studied in some detail. Because the only interpretational aids available previously were scale model results for conductors in free space, the results presented here should be useful in interpreting data and in designing new EM systems. As expected, anomalies decay rapidly as depth of burial is increased, due to attenuation in the conductive half‐space. Depth of exploration appears to be greatest for measurements of horizontal magnetic field phase, while vertical field phase is diagnostic of conductivity. Horizontal location and depth of burial are best determined through measurements of vertical or horizontal magnetic field amplitude.

scholarly journals Electromagnetic Reflection from Multi-Layered Models

1975 ◽  
Vol 15 (73) ◽  
pp. 462 ◽  
Author(s):  
William I. Linlor
Keyword(s):  
Water Resource Management ◽  
Plane Waves ◽  
Electromagnetic Response ◽  
Flood Prediction ◽  
Incident Plane ◽  
Arbitrary Thickness ◽  
Physical Attributes ◽  
Lossy Media ◽  
Practical Nature ◽  
Layered Models

The remote sensing of snowpack depth, density, and wetness with an airborne system would have important applications in water resource management and flood prediction. In this paper, the electromagnetic response of multi-layered models is analyzed. Normally-incident plane waves are assumed at frequencies ranging from 106 to 1010 Hz, and reflection amplitudes are calculated for models having various layer combinations. Each layer can have arbitrary thickness, and its own dielectric constant and conductivity, each of which can vary with frequency. Thus “lossy” media as well as “perfect” dielectrics can be employed in the models. An outline of the theory for the calculations is presented for an n-layered model. Because of the complexity of the equations, interpretation is accomplished by illustrative models, selected from seven snow types and seven earth types. The objective of this type of calculation is to establish the dependence of the reflection coefficient on the impedance transitions between two half-spaces. This paper is a theoretical study only, and does not include consideration of the size, weight, estimated cost, and other physical attributes of a flight system. These, and other matters of a practical nature, are being treated in other papers. A revised version of this paper is being published in full in another issue of the Journal of Glaciology.

MEASUREMENTS OF ANISOTROPIC PLASMAS USING A TURNSTILE MULTIPLE-PROBE POLARIMETER

1966 ◽  
Vol 44 (7) ◽  
pp. 1649-1662
Author(s):  
M. P. Bachynski ◽  
F. J. F. Osborne ◽  
B. W. Gibbs
Keyword(s):  
Magnetic Field ◽  
Plasma Diagnostics ◽  
Plane Waves ◽  
Time Varying ◽  
Microwave Frequencies ◽  
Circularly Polarized ◽  
Incident Plane ◽  
Linearly Polarized ◽  
Multiple Probe ◽  
Plasma Measurements

A turnstile multiple-probe polarimeter has been designed for plasma diagnostics at microwave frequencies. With the polarimeter, it is possible to measure simultaneously the amplitude and phase of the space quadrature components of an electromagnetic wave of arbitrary polarization. This technique is thus well suited for determining the properties of time-varying or steady-state anisotropic plasmas. Measurements have been conducted at a frequency of 9.2 Gc on a helium afterglow in a magnetic field, using both linearly polarized and circularly polarized incident plane waves. The agreement of these experiments with theory indicates that the multiple-probe polarimeter can be a reliable tool for plasma measurements.

scholarly journals Electromagnetic Reflection from Multi-Layered Snow Models

1975 ◽  
Vol 14 (72) ◽  
pp. 501-515 ◽  
Author(s):  
William I. Linlor ◽  
George R. Jiracek
Keyword(s):  
Water Resource Management ◽  
Plane Waves ◽  
Electromagnetic Response ◽  
Effective Dielectric Constant ◽  
Reflection Coefficients ◽  
Snow Layer ◽  
Flood Prediction ◽  
Incident Plane ◽  
Simplifying Assumptions ◽  
Amplitude Reflection

The remote sensing of snow-pack characteristics with surface installations or an airborne system could have important applications in water-resource management and flood prediction. To derive some insight into such applications, the electromagnetic response of multi-layered snow models is analyzed in this paper. Normally incident plane waves at frequencies ranging from 106 to 1010 Hz are assumed, and amplitude reflection coefficients are calculated for models having various snow-layer combinations, including ice layers. Layers are defined by a thickness, permittivity, and conductivity; the electrical parameters are constant or prescribed functions of frequency. To illustrate the effect of various layering combinations, results are given in the form of curves of amplitude reflection coefficients versus frequency for a variety of models. Under simplifying assumptions, the snow thickness and effective dielectric constant can be estimated from the variations of reflection coefficient as a function of frequency.

scholarly journals Electromagnetic Reflection from Multi-Layered Snow Models

1975 ◽  
Vol 14 (72) ◽  
pp. 501-515
Author(s):  
William I. Linlor ◽  
George R. Jiracek
Keyword(s):  
Water Resource Management ◽  
Plane Waves ◽  
Electromagnetic Response ◽  
Effective Dielectric Constant ◽  
Reflection Coefficients ◽  
Snow Layer ◽  
Flood Prediction ◽  
Incident Plane ◽  
Simplifying Assumptions ◽  
Amplitude Reflection

The remote sensing of snow-pack characteristics with surface installations or an airborne system could have important applications in water-resource management and flood prediction. To derive some insight into such applications, the electromagnetic response of multi-layered snow models is analyzed in this paper. Normally incident plane waves at frequencies ranging from 106 to 1010 Hz are assumed, and amplitude reflection coefficients are calculated for models having various snow-layer combinations, including ice layers. Layers are defined by a thickness, permittivity, and conductivity; the electrical parameters are constant or prescribed functions of frequency. To illustrate the effect of various layering combinations, results are given in the form of curves of amplitude reflection coefficients versus frequency for a variety of models. Under simplifying assumptions, the snow thickness and effective dielectric constant can be estimated from the variations of reflection coefficient as a function of frequency.

THE ELECTROMAGNETIC FIELDS OF A SUBTERRANEAN CYLINDRICAL INHOMOGENEITY EXCITED BY A LINE SOURCE

Geophysics ◽  
1972 ◽  
Vol 37 (6) ◽  
pp. 975-984 ◽  
Author(s):  
Allen Q. Howard
Keyword(s):  
Magnetic Field ◽  
Integral Equation ◽  
Line Source ◽  
Field Amplitude ◽  
Two Dimensional ◽  
Vertical Magnetic Field ◽  
Geophysical Prospecting ◽  
Field Phase ◽  
Horizontal Magnetic Field ◽  
Mine Rescue

The anomalous fields from a buried cylindrical inhomogeneity in an otherwise uniform half‐space are analyzed. The problem is rendered two‐dimensional by assuming that the uniform line source of current is parallel to the subsurface cylinder. The multipole scattered field coefficients are obtained from the numerical solution to the associated singular Fredholm integral equation of the second kind. The horizontal magnetic field amplitude, the vertical magnetic field phase, and the amplitude and phase of the ratio of horizontal to vertical magnetic fields are shown to be diagnostic of the location of the inhomogeneity. The results have possible applications to electromagnetic location in mine rescue operations and to geophysical prospecting.

Tensor CSAMT studies at the Buchans Mine in central Newfoundland

Geophysics ◽  
1993 ◽  
Vol 58 (1) ◽  
pp. 12-19 ◽  
Author(s):  
D. E. Boerner ◽  
J. A. Wright ◽  
J. G. Thurlow ◽  
L. E. Reed
Keyword(s):  
Magnetic Field ◽  
Electric Fields ◽  
Vertical Magnetic Field ◽  
Magnetic Field Data ◽  
Layered Earth ◽  
Reflection Seismic ◽  
Conductivity Structure ◽  
Geophysical Study ◽  
Orthogonal Components ◽  
Strong Scattering

A novel application of the tensor controlled source audio‐magnetotelluric (CSAMT) method was part of a multidisciplinary geophysical study of an existing mine site at Buchans, Newfoundland. The orthogonal components of the horizontal electromagnetic fields used for magnetotelluric and CSAMT interpretation of the earth’s conductivity structure were found to be inappropriate at Buchans because of strong scattering in the electric fields. Instead, the length of the major axes of the electric and magnetic field polarization ellipses and the vertical magnetic field were used as data. The data from two bipole sources demonstrate that the bulk response of the earth in the vicinity of Buchans is predominantly one‐dimensional (1-D). These data were inverted to layered earth models with a first‐order correction for electric field distortions. The parameter space considered during the inversion was contracted substantially by incorporating the vertical magnetic field data and by using depths to interfaces as determined by reflection seismic data. The model resulting from the inversions is essentially a two‐layered earth with an increase in resistivity between 1000–1400 m depth. The contrast in the electrical properties is interpreted to be coincident with the Powerline Fault, a floor thrust of a duplex structure with significant out‐of‐sequence movement. Hence, the thrusting may have caused the emplacement of older fractured, and locally mineralized rocks over younger more competent (resistive) ones.

scholarly journals Electromagnetic Reflection from Multi-Layered Models

1975 ◽  
Vol 15 (73) ◽  
pp. 462-462
Author(s):  
William I. Linlor
Keyword(s):  
Water Resource Management ◽  
Plane Waves ◽  
Electromagnetic Response ◽  
Flood Prediction ◽  
Incident Plane ◽  
Arbitrary Thickness ◽  
Physical Attributes ◽  
Lossy Media ◽  
Practical Nature ◽  
Layered Models

The remote sensing of snowpack depth, density, and wetness with an airborne system would have important applications in water resource management and flood prediction. In this paper, the electromagnetic response of multi-layered models is analyzed. Normally-incident plane waves are assumed at frequencies ranging from 106 to 1010 Hz, and reflection amplitudes are calculated for models having various layer combinations. Each layer can have arbitrary thickness, and its own dielectric constant and conductivity, each of which can vary with frequency. Thus “lossy” media as well as “perfect” dielectrics can be employed in the models. An outline of the theory for the calculations is presented for an n-layered model. Because of the complexity of the equations, interpretation is accomplished by illustrative models, selected from seven snow types and seven earth types. The objective of this type of calculation is to establish the dependence of the reflection coefficient on the impedance transitions between two half-spaces. This paper is a theoretical study only, and does not include consideration of the size, weight, estimated cost, and other physical attributes of a flight system. These, and other matters of a practical nature, are being treated in other papers.A revised version of this paper is being published in full in another issue of the Journal of Glaciology.

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