Controlled Artificial Generation of Ultra-Low-Frequency Hydromagnetic Waves in the Ionosphere and Magnetosphere PDF Download
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Author: O. G Villard (Jr)
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Category :
Languages : en
Pages : 20
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This report summarizes theoretical and experimental work sponsored by the Defense Advanced Projects Agency at Stanford University through the Office of Naval Research Contract No. N00014-75-C-1095. The primary purpose of this work, which was conducted during the interval 1 January 1975 through 28 February 1977, was to investigate the possibility of obtaining a relatively inexpensive method for the controlled artificial generation of ultra-low-frequency (ULF; frequencies less than 5 Hz) geomagnetic pulsations. Because of the great penetration of these signals in sea water, the controlled artificial source could conceivably be used as a transmitter to communicate with deeply submerged receivers at a low data rate. A second purpose of the work was to investigate the feasibility of using airborne loop antennas for air/undersea communication at ULF. The following are the major conclusions of this work; (1) The controlled artificial generation of ULF geomagnetic pulsations by the 'peninsula method, ' i.e., by the passage of a ULF-modulated electric current around a relatively nonconducting peninsula in the sea or in a large saline lake, is feasible and that further experiments, in particular, a fullscale ULF wave generation experiment, appear desirable. (2) The controlled artificial generation of ULF geomagnetic pulsations by the 'VLF method, ' i.e., by the injection of ULF-modulated VLF signals into the magnetosphere from a large ground-based VLF transmitter, appears possible, but further theoretical and experimental studies are required to clarify the generation mechanism.
Author: O. G Villard (Jr)
Publisher:
ISBN:
Category :
Languages : en
Pages : 20
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Book Description
This report summarizes theoretical and experimental work sponsored by the Defense Advanced Projects Agency at Stanford University through the Office of Naval Research Contract No. N00014-75-C-1095. The primary purpose of this work, which was conducted during the interval 1 January 1975 through 28 February 1977, was to investigate the possibility of obtaining a relatively inexpensive method for the controlled artificial generation of ultra-low-frequency (ULF; frequencies less than 5 Hz) geomagnetic pulsations. Because of the great penetration of these signals in sea water, the controlled artificial source could conceivably be used as a transmitter to communicate with deeply submerged receivers at a low data rate. A second purpose of the work was to investigate the feasibility of using airborne loop antennas for air/undersea communication at ULF. The following are the major conclusions of this work; (1) The controlled artificial generation of ULF geomagnetic pulsations by the 'peninsula method, ' i.e., by the passage of a ULF-modulated electric current around a relatively nonconducting peninsula in the sea or in a large saline lake, is feasible and that further experiments, in particular, a fullscale ULF wave generation experiment, appear desirable. (2) The controlled artificial generation of ULF geomagnetic pulsations by the 'VLF method, ' i.e., by the injection of ULF-modulated VLF signals into the magnetosphere from a large ground-based VLF transmitter, appears possible, but further theoretical and experimental studies are required to clarify the generation mechanism.
Author: A. C. Fraser-Smith
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Category :
Languages : en
Pages : 46
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This report presents the results of an investigation of a proposed method for the controlled artificial generation of ultra-low-frequency (ULF) hydromagnetic waves, primarily of class Pc 1 (0.2 to 5 Hz), in the ionosphere and magnetosphere. The basis of this method, which is called the 'peninsula method' (a second possible method, the 'VLF method', is discussed in a companion report), is the passage of a ULF-modulated electric current around a relatively nonconducting peninsula in the sea or in a large saline lake to form a ULF current loop that produces a ULF magnetic field in the lower ionosphere. Provided the amplitude of the ULF magnetic field fluctuations is sufficiently large, i. e., provided the maximum magnetic moment of the peninsula current loop is greater than about 10 to the 13th power Am2, it is predicted theoretically that ULF hydromagnetic waves can be generated in a disturbed region of the lower ionosphere above the peninsula. These waves can then propagate away to large distances in the ionosphere and magnetosphere. The peninsula method is a version of a particular class of ULF wave generation methods based on the use of large ground-based ULF current systems. Compared with other possible methods of generation, these methods appear to have the advantage of reliability and versatility. However, both the construction costs and the power requirements for these systems are large.
Author: A. C. Fraser-Smith
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ISBN:
Category :
Languages : en
Pages : 64
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This report presents the results of an investigation of a proposed method for the controlled artificial generation of ultra-low-frequency (ULF) hydromagnetic waves of class Pc 1 (0.2 to 5 Hz) in the ionosphere and magnetosphere. In this method, which is called the VLF method, a large ground-based very-low-frequency (VLF) transmitter is used to stimulate the ULF waves by injecting pulses of VLF waves into the magnetosphere. A second possible method of ULF wave generation, the peninsula method, is discussed in a companion report. Combining the theoretical and experimental results obtained during this research, it is suggested that naturally-occurring repetitive VLF activity can stimulate Pc 1 pulsation events, and it is further suggested that such VLF activity may be a major source of stimulation for Pc 1 pulsations. Thus, future experiments on ULF wave generation with ground-based VLF transmitters would probably benefit greatly if they were combined with a program of simultaneous observations of naturally-occurring VLF and ULF activity.
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Category : Aeronautics
Languages : en
Pages : 1134
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Category : Power resources
Languages : en
Pages : 1212
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Semiannual, with semiannual and annual indexes. References to all scientific and technical literature coming from DOE, its laboratories, energy centers, and contractors. Includes all works deriving from DOE, other related government-sponsored information, and foreign nonnuclear information. Arranged under 39 categories, e.g., Biomedical sciences, basic studies; Biomedical sciences, applied studies; Health and safety; and Fusion energy. Entry gives bibliographical information and abstract. Corporate, author, subject, report number indexes.
Author: S. P. Kuo
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Category :
Languages : en
Pages : 121
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The topics of investigation are divided into four general categories: (a) cavity modes of the magnetosphere resulting in the discrete spectrum of the resonant ultralow frequency waves; (b) a hydromagnetic code for the numerical study of the coupling of hydromagnetic waves in the dipole model of the magnetosphere; a theoretical model developed for explaining the phenomenon of plasma line over shoot observed in the ionospheric HF heating experiments; and thermal flamentation instability as the mechanism for generation of large scale field aligned ionospheric irregularities. For the first two topics, the hydromagnetic wave equations are analyzed analytically in cylindrical model of the magnetosphere and numerically in dipole model of the magnetosphere, respectively. While the steady state eigenvalue problem is studied in the first topic, the second topic is generalized to the boundary value problem considering the coupling between hydromagnetic waves in the realistic geometry of the magnetosphere. For the third topic, a nonlinear turbulent theory (resonance instability excited by a powerful high frequency in the ionosphere. For the last topic, the thermal nonlinearity gives rise to the mode-mode coupling; threshold field and the growth rate of the instability are derived. (jhd).
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Category : Power resources
Languages : en
Pages : 600
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Author: Stanford Electronics Laboratory
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Category :
Languages : en
Pages : 134
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Author: Muhammad Abbas
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Category : Magnetohydrodynamics
Languages : en
Pages : 125
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The report is concerned with the analysis of hydromagnetic waves which are generated in various regions of the magnetosphere and propagated to the earth in the extremely low frequency spectrum. Two different aspects of the problem are investigated, namely, propagation through inhomogeneous regions of the ionosphere and propagation and excitation of waves in current carrying regions of the ionosphere and the magnetosphere. Propagation through inhomogeneous regions is studied by two different methods: Transmission coefficients for hydromagnetic waves are obtained by assuming a linearly varying inhomogeneous region and by transforming the wave equation into a hypergeometric equation such that various types of inhomogeneities can be handled (Epstein theory). Assuming a hydromagnetic wave incident from above and propagating parallel to the earth's magnetic field, power transmission coefficients are calculated for various times of day. Propagation of hydromagnetic waves through a current carrying plasma is investigated on the basis of macroscopic equations in which additional terms arising from the presence of a constant current density are included. A general dispersion relation for small amplitude waves is derived. For propagation normal to the steady magnetic field, when the currents are normal to both, the direction of propagation and the static magnetic field, it is found that amplification takes place. For longitudinal propagation with currents in the transverse plane, the propagation constant remains unaffected. For longitudinal propagation, with currents also along the direction of propagation, the propagation constant has a resonance at the ion-cyclotron frequency for both, right and left hand polarization. (Author).
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Category : Government reports announcements & index
Languages : en
Pages : 1728
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