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  • 1
    Electronic Resource
    Electronic Resource
    Analysis of microwave ducting in an inhomogeneous troposphere (1978)
    Springer
    Pure and applied geophysics 116 (1978), S. 1118-1142 
    Details
    ISSN: 1420-9136
    Keywords: Electromagnetic waves ; transmission of in troposphere ; Microwaves ; transmission of in troposphere
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Summary Theory for the transmission of electromagnetic waves in a non-uniform troposphere is presented. The atmospheric refractive index is allowed to vary both with height and range. The formulation is facilitated by the fact that the field within a piecewise (laterally) uniform section can be represented by a discrete sum of modes that are orthogonal in the transverse plane. Using the appropriate radial wave functions, mode conversion at a junction between two laterally uniform sections is considered. The analysis is then extended to multi-section structures. A few typical profiles of refractive index are examined numerically for both uniform and non-uniform models. One of the important findings is that the lateral non-uniformities in an elevated duct will enhance the overall transmission for ground-based transmitting and receiving antennas.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00874676
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  • 2
    Electronic Resource
    Electronic Resource
    Analysis of the earth resistivity response of buried cables (1978)
    Springer
    Pure and applied geophysics 117 (1978), S. 711-742 
    Details
    ISSN: 1420-9136
    Keywords: Resistivity ; Conductors in earth ; Buried Cables ; Direct Current
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Current flow in homogeneous and layered conducting media is analyzed for the case where an axial conductor or cable is present. The cable is characterized by a specified axial impedance and is assumed to be infinite in length. Various configurations are chosen such as a current point source in an infinite, semi-infinite, and layered region where the cable is taken parallel to the interface(s). The resulting formulas for the potentials reduce to known cases in the absence of the cable. Using these formulations, we present some concrete calculated examples that are relevant to resistivity probing of perturbed homogeneous and layered structures. Only the two-electrode array is treated, but various cable orientations are considered. In general, it is found that a long axial conductor such as a bare cable will distort the potential distribution of the current in a major way. This leads to profound departures from the apparent resistivity curves calculated for idealized homogeneous and layered structures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00879975
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  • 3
    Electronic Resource
    Electronic Resource
    Resistivity and induced polarization response of a thin sheet (1985)
    Springer
    Pure and applied geophysics 123 (1985), S. 882-892 
    Details
    ISSN: 1420-9136
    Keywords: thin sheet ; induced polarization ; resistivity ; borehole ; conductive slab ; dilution factor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The relevant potential theory is given for a current point source in the presence of a conductive slab embedded in a homogeneous host region of infinite extent. The thin sheet representation is obtained from the exact integral formulation by a simple mathematical limit process. The same result is also deduced directly at the outset by applying a thin sheet boundary condition. The apparent resistivity for a two electrode array is then computed for the case where the bore hole intersects the thin sheet at right angles. The corresponding results for the dilution factor, relevant to the induced polarization response, are also obtained. It is shown that the apparent resistivity and the dilution factor are constant when the potential and the current electrode straddle the sheet but there is a characteristic decrease as the electrodes move away from the sheet.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00876976
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  • 4
    Electronic Resource
    Electronic Resource
    On the mode theory of V. L. F. ionospheric propagation (1957)
    Springer
    Pure and applied geophysics 37 (1957), S. 103-115 
    Details
    ISSN: 1420-9136
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Summary The space between the earth and the ionosphere is considered as a wave-guide with sharply bounded walls. Employing a representation in terms of spherical wave functions of complex order, the field of a vertical dipole source is calculated for very low frequencies. It is shown that the dominant mode for 16 kc is of order one and not zero as has been commonly supposed. Good agreement is obtained with the experimental results ofJ. Heritage.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01988854
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  • 5
    Electronic Resource
    Electronic Resource
    Theory of electromagnetic surface waves over geological conductors (1954)
    Springer
    Pure and applied geophysics 28 (1954), S. 47-56 
    Details
    ISSN: 1420-9136
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Summary The radiation fields of a vertical electric antenna situated on a horizontally stratified ground are discussed. The attenuation and “wave-tilt” of the surface wave and the “height-gain” factor are shown to be a function of the horizontal stratification in the ground. It is possible that the results have application to an airborne geophysical exploration scheme.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01992391
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  • 6
    Electronic Resource
    Electronic Resource
    Theory of the electromagnetic transient response of the ionosphere for plane wave excitation (1971)
    Springer
    Pure and applied geophysics 90 (1971), S. 169-186 
    Details
    ISSN: 1420-9136
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Summary The reflection and transmission of a transient plane wave by an ionosphere with a linear electron density profile and constant collision frequency are calculated. The exact frequency domain solution is inverted numerically, and the resultant reflected and transmitted waveforms are found to satisfy causality. A linearly varying, nondispersive dielectric half-space is also considered, but the nonphysical nature of the model causes the reflected waveform to be noncausal. Using convolution the waveforms for a step modulated sinusoid excitation are also obtained from the impulse response of the ionosphere. The results provide insight into the physical mechanism involved in the ionospheric propagation of HF electromagnetic pulsed signals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00875521
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  • 7
    Electronic Resource
    Electronic Resource
    Electromagnetic propagation in an idealized earth crust waveguide, part I (1972)
    Springer
    Pure and applied geophysics 101 (1972), S. 174-187 
    Details
    ISSN: 1420-9136
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Summary The electromagnetic mode characteristics for the earthcrust waveguide are considered. The formulation allows for any depth-conductivity profile, but the specific results are only for a homogeneous sub-surface waveguide region with a finitely conducting lower layer and a perfectly conducting upper layer. Attenuation rates of the order of 1 dB/km are possible for operating frequencies of 20 kHz or lower if the crystalline rock in the waveguide has conductivities less than 10−6 mhos per meter.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00876781
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  • 8
    Electronic Resource
    Electronic Resource
    Electromagnetic transient response of a small wire loop buried in a homogeneous conducting earth (1973)
    Springer
    Pure and applied geophysics 105 (1973), S. 869-878 
    Details
    ISSN: 1420-9136
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Summary The analysis extends previously obtained results for the transient magnetic fields of small loops in the presence of a homogeneous conducting half-space. Here, the secondary scattering of pulses by a buried target loop is examined for the case where both the source and receiver loops are located at the surface. While the response of the buried or target loop is orders of magnitude below the primary response, there is a significant difference in the respective transient waveforms. Thus, the results have possible application to mine rescue using a passive detection technique.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00875836
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  • 9
    Electronic Resource
    Electronic Resource
    On calculating transient electromagnetic fields of a small current-carrying loop over a homogeneous earth (1972)
    Springer
    Pure and applied geophysics 95 (1972), S. 157-162 
    Details
    ISSN: 1420-9136
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Summary The basic theory of airborne EM surveying, in the time domain, is considered. Rather than resorting to tediousdouble numerical integration, a more direct approach is adopted. This method, valid in the quasi-static regime, is illustrated for a homogeneous flat earth. The results exhibit a number of clear-cut features that are relevant to remote sensing. For example, a vertical co-axial loop system has a desirable transient response from the standpoint of yielding conductivity data without requiring accurate information on the height of the device above the ground.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00878864
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  • 10
    Electronic Resource
    Electronic Resource
    Some basic electromagnetic aspects of ULF field variations in the atmosphere (1976)
    Springer
    Pure and applied geophysics 114 (1976), S. 15-28 
    Details
    ISSN: 1420-9136
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Recent analytical studies of ULF (ultra low frequency) electromagnetic fields in the atmosphere are reviewed. These fields have their origin in the discharging of thunderclouds and the interaction with the conductive atmosphere determines the resultant behavior. It is important that this interaction process be understood if observations are to be correctly interpreted in terms of the thunderstorm discharge process. Various theoretical approaches that have appeared in the literature are appraised and suggestions for further work are made.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00875488
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