The Effects of Ground-based Very Low Frequency Transmitters on the Ionosphere and Magnetosphere PDF Download
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Author: Kevin Graf
Publisher:
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Category :
Languages : en
Pages :
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The effects of ground-based very low frequency (VLF) transmitters on the ionosphere and magnetosphere are investigated. VLF transmitters, used primarily for Naval communications with submarines, are also capable of heating the ionosphere and inducing the precipitation of energetic electrons from the Earth's radiation belts. Controlled modulation experiments are performed with the 21.4 kHz, 424 kW VLF transmitter NPM in Lualualei, Hawaii, and physical effects of the NPM transmissions are studied with sub-ionospherically propagating VLF probe signals. Observed perturbations to the probe signal are not consistent with expectations from transmitter-induced electron precipitation nor to off-path scattering from a concentrated heating region near the transmitter but rather appear to be the result of scattering from extended lateral heating of the ionosphere by the NPM transmitter. A large-scale computational modeling framework confirms theoretically that this form of ionospheric heating can account for the observed probe signal modulations, establishing that the lateral extent of ionospheric heating due to VLF transmitters is several thousand kilometers, significantly greater than previously recognized. The trans-ionospheric propagation of VLF waves is also investigated as updated attenuation estimates are provided for multiple scenarios.
Author: Kevin Graf
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
The effects of ground-based very low frequency (VLF) transmitters on the ionosphere and magnetosphere are investigated. VLF transmitters, used primarily for Naval communications with submarines, are also capable of heating the ionosphere and inducing the precipitation of energetic electrons from the Earth's radiation belts. Controlled modulation experiments are performed with the 21.4 kHz, 424 kW VLF transmitter NPM in Lualualei, Hawaii, and physical effects of the NPM transmissions are studied with sub-ionospherically propagating VLF probe signals. Observed perturbations to the probe signal are not consistent with expectations from transmitter-induced electron precipitation nor to off-path scattering from a concentrated heating region near the transmitter but rather appear to be the result of scattering from extended lateral heating of the ionosphere by the NPM transmitter. A large-scale computational modeling framework confirms theoretically that this form of ionospheric heating can account for the observed probe signal modulations, establishing that the lateral extent of ionospheric heating due to VLF transmitters is several thousand kilometers, significantly greater than previously recognized. The trans-ionospheric propagation of VLF waves is also investigated as updated attenuation estimates are provided for multiple scenarios.
Author: Wenyao Gu
Publisher:
ISBN:
Category : Physics
Languages : en
Pages : 0
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Signals from ground-based very low frequency (VLF) transmitters can leak through the ionosphere and propagate in the inner magnetosphere as whistler-mode waves. They interact with energetic electrons from the Earth’s radiation belts, and precipitate them into the ionosphere. The effect of wave-particle interactions is affected by signal propagations, which depend on the spatial variation of the cold plasma population (as the propagation medium). Therefore, a further understanding of transmitter signal propagation and cold plasma medium is essential for investigating wave-particle interactions. First, a case study is performed on Russian Alpha transmitter signals observed by the Van Allen Probes. The signals are in ducted propagation, experience multiple reflections, and excite triggered emissions. The ducted propagation is justified by a ray-tracing technique, and the nonlinear cyclotron resonance theory is tested by the observed triggered emissions. Second, we perform a statistical study on the distribution of the two propagation modes, ducted and nonducted, by the use of observed Russian Alpha transmitter signals. The statistics show the dominance of nonducted signals in the plasmasphere in terms of both occurrence and power. The proportion of ducted signals is enhanced at higher L-shells and during active geomagnetic conditions. Finally, we statistically analyze the spatial and temporal distributions of inner-magnetospheric cold plasma density irregularities, which are responsible for ducted propagation. The density irregularities deep inside the plasmasphere are dominant in the night and dusk sectors and show no significant variation with geomagnetic conditions. In contrast, the density irregularities in and near the plasmasphere boundary layer occur at post-midnight during quiet times and expand throughout the night sector during active times.
Author: A. C. Fraser-Smith
Publisher:
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.
Author: Robert A. Helliwell
Publisher: Courier Corporation
ISBN: 0486151212
Category : Technology & Engineering
Languages : en
Pages : 370
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The investigation of whistlers and related phenomena is a key element in studies of very-low-frequency propagation, satellite communication, the outer ionosphere, and solar-terrestrial relationships. This comprehensive text presents a history of the study of the phenomena and includes all the elements necessary for the calculation of the characteristics of whistlers and whistler-mode signals. An introduction and brief history are followed by a summary of the theory of whistlers and a detailed explanation of the calculation of their characteristics. Succeeding chapters offer a complete atlas of a variety of whistlers, including those observed in satellites and those generated by nuclear explosions; the results of satellite observation of whistler-mode propagation; the method of reducing whistler data and obtaining electron density information; a full atlas of the various kinds of emissions; and an outline and comparison of the theories of generation of emissions.
Author: Committee on the Role of High-Power, High-Frequency-Band Transmitters in Advancing Ionospheric/Thermospheric Research: A Workshop
Publisher: National Academies Press
ISBN: 9780309298599
Category : Science
Languages : en
Pages : 63
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Opportunities for High-Power, High-Frequency Transmitters to Advance Ionospheric/Thermospheric Research is the summary of a workshop convened by the Space Studies Board of the National Research Council in May 2013. The request for this workshop was informed by the sponsors' awareness of the possibility that tight budgets would result in the Department of Defense's curtailment or even termination1 of support for the High Frequency Active Auroral Research Program (HAARP), which includes the world's highest-power and most capable high-frequency transmitter - "heater" - for ionospheric research. Although the workshop was organized to consider the utility of heaters in upper atmospheric research in general, it had a specific focus on the HAARP transmitter facility, which is located in a remote part of southeastern Alaska. Research conducted by the ionospheric modifications community - a community that uses high-frequency transmitters to inject energy in the ionosphere and measure its effects using ground and space-based diagnostics - is focused on understanding the interaction of radio waves with the ionospheric plasma, the local consequences of heating in the ionosphere, and studies of non-linear plasma physics processes. The workshop provided a forum for information exchange between the comparatively small group of scientists engaged in programs of upper atmospheric research using high-power high-frequency radar transmitters and the larger ionospherethermosphere-magnetosphere research community. This report examines the state of the art in active ionospheric and thermospheric research; considers the fundamental research areas in ionospheric science that can be addressed using high-power high-frequency-band transmitters; discusses emerging science questions that might benefit from active ionospheric experiments in the sub-auroral zone; and considers ways to combine similar facilities to perform global ionospheric science. The report also examines research opportunities that might arise from the relocation of the AMISR incoherent scatter radar from the Poker Flat Research Facility in Poker Flat, AK to Gakona, AK, the location of the HAARP facility.
Author: A. R. W. Hughes
Publisher: Alpha Science Int'l Ltd.
ISBN: 9788173194856
Category : Science
Languages : en
Pages : 390
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Contributed articles presented at the Workshop.
Author: O. G Villard (Jr)
Publisher:
ISBN:
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: United States. National Bureau of Standards
Publisher:
ISBN:
Category : Radio
Languages : en
Pages : 816
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Author: United States. National Bureau of Standards
Publisher:
ISBN:
Category : Ionospheric radio wave propagation
Languages : en
Pages : 1400
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Author:
Publisher:
ISBN:
Category : Power resources
Languages : en
Pages : 1344
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