WorldCat Identities

Davidson, G. T.

Overview
Works: 10 works in 12 publications in 1 language and 12 library holdings
Genres: Academic theses 
Roles: Author
Classifications: QC881.2.I6,
Publication Timeline
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Most widely held works by G. T Davidson
A Space Radiation Test Model Study( Book )

2 editions published between 1986 and 1989 in English and held by 2 WorldCat member libraries worldwide

Dynamic models of the energetic populations in the outer radiation belts are being developed to better understand the extreme variations of particle flux in response to magnetospheric and solar activity. The study utilizes the SCATHA SC3 high energy electron data, covering energies from 47 keV to 5 MeV with fine pitch angle measurements (3 deg field of view) over the L-shell range of 5.3 to 8.7. Butter-fly distributions in the dusk sector signify particle losses due to L shell splitting of the particle drift orbits and the subsequent scattering of the particles from the orbits by the magnetopause. To model the temporal variations and diffusion procsses of the particle populations, the data have been organized into phase space distributions, binned according to altitude (L shell), energy, pitch angle, and time. These distributions can then be mapped to the equator and plotted for fixed first and second adiabatic invariants of the inherent particle motion. A new and efficient method for calculating the third adiabatic invariant using a line integral of the relevant magnetic potential at the particle mirror points has been developed and is undergoing testing. This method will provide a useful means of displaying the radial diffusion signatures of the outer radiation belts during the more active periods when the L shell parameter is not a good concept due to severe drift-shell splitting. The first phase of fitting the energetic electron phase-space distributions with a combined radial and pitch-angle diffusion formulation is well underway. Bessel functions are being fit to the data in an eigenmode expansion method to determine the diffusion coefficients
Investigation of Phenomena Affecting Auroral Ionosphere( Book )

1 edition published in 1974 in English and held by 2 WorldCat member libraries worldwide

Rocket data obtained during a magnetic substorm on 16 August 1970 indicates the auroral ionosphere was unstable to the high-frequency, Hall current, two stream instability. This mechanism has been proposed to explain field-aligned ionospheric irregularities. Such irregularities were present during the rocket experiment. According to the theory, certain critical values of electron number density, current density, and relative electron-ion drift velocity must be exceeded for the instability to occur. An analysis is described in which calculated values of these quantities are derived from the rocket measurements of the dc electric field and the precipitating electrons. The results are found to exceed the respective critical values and enforce the conclusion that the field-aligned irregularities were produced by this instability. (Modified author abstract)
Investigation of ionospheric disturbances( )

1 edition published in 1977 in English and held by 1 WorldCat member library worldwide

Methods are described for solving the diffusion equation for trapped particles precipitating in the ionosphere. It is shown that the variation of the particle distribution with spatial location, both latitudinal and longitudinal, must be considered, and that the bounce averaged diffusion equations are inadequate to treat the loss-cone distributions. The coupling of precipitating particles to the ionosphere is described, with applications of the AURORA code. Mid-latitude WIDEBAND observations are described, with a discussion of interpretations based on trapped particle precipitation. Recent observations are described of loss-cone distributions of ions and electrons which do not fit the simple diffusion model. It is shown that these observations can be accounted for by the presence of kilovolt electric fields aligned with the magnetic field. It is shown that the ionosphere at large distances from a high-altitude nuclear explosion may be unstable to the Farley-Buneman mechanism, thereby providing a new mechanism for ionospheric irregularities
Ionospheric Effects Resulting from Precipitating Electrons at Mid and High Latitudes( Book )

1 edition published in 1976 in English and held by 1 WorldCat member library worldwide

The distributions of electrons resulting from pitch-angle diffusion due to both wave-particle interactions at high altitudes and binary collisions in the atmosphere have been determined. The results seem to be in agreement with available data, however wave fields which may be too high are required to fit the data. Some of the computational routines and cross sections used in the low-energy (1 eV to 500 eV) portion of the AURORA code have been improved. Processes occurring in the disturbed ionosphere other than collision and magnetic mirroring are inferred by comparing measurements of pitch-angle and energy distributions of electrons in the auroral zones with distributions computed with the AURORA code. (Author)
A district headquarters and police station, Durban by G. T Davidson( Book )

2 editions published in 1960 in English and held by 1 WorldCat member library worldwide

Assessment of Magnetospheric Processes of Importance in HANE( Book )

1 edition published in 1979 in English and held by 1 WorldCat member library worldwide

Conditions in the unstable field-aligned current sheet above the auroral oval have been obtained from analyses of the electron and ion measurements on the S3-3 satellite. The measurements were obtained while the satellite was in and near the nominal region of the current sheet, remaining within a few degrees in invariant latitude, over a magnetic local-time interval of about 6 hours. Potential differences along the magnetic field, above and below the satellite, were inferred from the energy and pitch-angle distributions of the electrons. These potential differences, which exceeded 10 kV at times, were generally higher during the local evening than during the local afternoon, and were quite variable along the satellite trajectory, indicating latitudinal fluctuations of the current sheet with periods of 2-7 minutes. Upward flowing H+ and O+ ions were observed whenever the potential differences exceeded about .5 kV, which corresponds to the lowest energy threshold of the detectors. However, the pitch-angle distributions of the ions imply that the ions were accelerated not only along the magnetic field by the potential difference, but also perpendicularly to the field. The transverse acceleration of the ions most probably occurred through interactions with electrostatic ion cyclotron (EIC) waves, which are an expected product of the current-driven instability, and which have been observed in the current-sheet region
Improvement of Specter II Code: Injection and Evolution of an Artificial Radiation Belt( Book )

1 edition published in 1979 in English and held by 1 WorldCat member library worldwide

Further improvements have been made in the SPECTER codes which compute the nuclear environment resulting from a high-altitude nuclear explosion and irradiation of satellites in that environment. A realistic model has been developed for the computation of fission-debris distribution in the magnetosphere. The model uses as input the distribution of debris and hot ionized air in the vicinity of the magnetic bubble. It computes the subsequent evolution of the distribution as the plasma expands along and across the magnetic field. The motion across the magnetic field is determined by using an equivalent LCR circuit to find the ionospheric currents, which neutralize the transverse polarization fields. For a yield larger than 1 Megaton it was found that the tube containing the debris was convected outward from an initial L of 1.16 to beyond the maximum L value for trapping
Magnetospheric Chemical Release Study( Book )

1 edition published in 1973 in English and held by 1 WorldCat member library worldwide

Wave particle interactions in the magnetosphere can produce ULF and VLF amplification, affect the diffusion of energy from the magnetosphere to the ionosphere, and may affect the trapping of energetic electrons and protons. Chemical releases of barium or lithium may modify the wave particle interactions in the magnetosphere such that the phenomena can be better investigated and may lead to techniques for producing desired wave particle interactions. Under this study results of a barium release in the outer magnetosphere and OGO-5 satellite results have been reviewed to obtain guidance in planning future satellite experiments. The possibility of using cold plasma chemical releases to reduce trapped betas from nuclear detonations has been studied. Data on previous observations of electrons and protons in the magnetosphere have been collected. General requirements for satellite experiments are given. (Author)
Assessment of Processes Related to Plasma Irregularities( Book )

1 edition published in 1977 in English and held by 1 WorldCat member library worldwide

The occurrence of plasma irregularities that affect radio-wave propagation is assessed both for naturally-occurring disturbances and for disturbances resulting from a high-altitude nuclear explosion. Data obtained with the S3-3 satellite reveal that high electrostatic potential differences - to 8 kV - with associated plasma irregularities, often occur along the magnetic field at high latitudes. In a detailed analysis of electron and ion pitch-angle and energy distributions measured on the satellite, the potential differences below and above the satellite, and the potential distribution above the satellite, were determined. The properties of the potential structure, together with concurrent observations of electrostatic waves, indicate that the potential is supported by anomalous resistivity. Analysis of the wideband data reveals that the scintillation activity has a spatial structure and occurrence similar to those of discrete auroral arcs and electric fields. The general morphology of the scintillations at high latitudes is described, and some interpretations of the data are suggested. The electric fields and currents induced by the debris plasma and fission beta-decay electrons in the magnetosphere due to a high-altitude nuclear explosion are estimated. For large bursts, the currents, both along and across the magnetic field, exceed well-established plasma-instability criteria, resulting in the formation of plasma irregularities. The region over which they are expected to occur extends as much as 60 deg in longitude east of the burst and, north of the burst, to latitudes near the auroral zone. (Author)
Ionospheric Effects Induced by Precipitating Auroral Electrons. HAES Report No. 14( Book )

1 edition published in 1975 in English and held by 1 WorldCat member library worldwide

The results of a coordinated experiment conducted in the auroral zone on 8 December 1971 were used to determine whether the AURORA computer code includes all of the important processes associated with the precipitation of electrons in the atmosphere. A precipitating electron flux was measured with the 1971-089A satellite simultaneously with ionospheric electron number-density distribution measurements using the Chatanika incoherent-scatter radar. The electron density distribution was compared with the distribution computed by the AURORA code, using the measured electron flux as input. The AURORA code was used to compute energy-deposition profiles in the atmosphere due to the precipitation of electrons released by high-altitude nuclear detonations
 
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Languages
English (12)