Thesis (Ph. D.)--University of Washington, 1988. / Vita. Bibliography: leaves [148]-156.

Thesis (Ph.D.)--University of Texas at Dallas, 2008. / Includes vita. Includes bibliographical references (leaves 105-110)

Thesis (Ph. D.)--University of Washington, 1996. / Vita. Includes bibliographical references (pages [181]-212).

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This thesis describes observations of the flne structure in Jovian decametric radiation made at Grahamstown during the 1967-68 apparition. It was found that pulses with duration less than 0.5 milliseconds were common during fine structure storms. The restrictions placed on the source for different theories of origin of the short pulses are discussed. The variation of the probability of occurrence from year to year is analysed on the assumption that the radiation is found in directions fixed with respect to the planet's magnetic field. It is concluded that there is a factor other than the declination of Earth and the Io effect which controls the probability of occurrence. A detailed analysis suggests a beam width of 3° in latitude at Jupiter but further work is necessary to check this.

Thesis (Ph.D.)--Boston University / PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you. / The Earth's magnetic cusps are the regions with the most direct transfer of energy, mass, and momentum from the flowing solar wind to the Earth's magnetosphere. Spacecraft observations in the cusp have revealed a high energy component to the thermal particle distribution. This has raised the question as to whether significant plasma heating may also be occurring in this region. Since the cusp is magnetically connected to a number of other regions in geospace, plasma heating in this region could be a significant contributor to magnetospheric dynamics. The goal of this thesis is to answer the question, what is the source of the energetic particle population in the cusp? Since the initial observations measuring the energetic component were made, the source of the energetic population has been open to conjecture. A number of sources have been proposed: (1) the terrestrial bow shock, (2) the Earth's high-latitude trapping region, and (3) heating of plasma locally in the cusp. Depending on which source is the dominant provider of the energetic particles, the particle population will exhibit different properties. Particle flow direction, intensity, spectral characteristics, and species/charge state are all properties that can change depending on the dominant source. In-situ measurements by the ISEE, Polar, and Cluster spacecraft are used to derive the particle properties. These properties are compared with predictions for each of the proposed sources to determine which is most consistent with the observations. Case studies show that, under different conditions, the high-latitude trapping region and local heating can both be the dominant source of the energetic particle population up to energies of hundreds of keV. Results from a large scale statistical study, however, are more consistent with local heating indicating that this is the dominant source the majority of the time. / 2999-01-01

Earth's ionosphere is a region of the upper atmosphere that consists of an energetic and electromagnetically reactive plasma. This region plays an important role in over-the-horizon and satellite radio communications, satellite orbits, and can electrically couple into human infrastructure like pipelines and power cables. Activity in the ionosphere is tightly coupled to the near-Earth space plasma region called the magnetosphere. This region is formed by interactions between the energetic particle outflow from the sun called the Solar Wind and Earth's magnetic field. Models of the coupling between these regions typically take a "sun to mud" perspective, as mass and energy from the sun are transferred into the magneto- sphere and ultimately into the upper atmosphere. However, the ionosphere also receives energy directly from ultra-violet radiation from the solar surface. This radiation is the nominal source of ionization in the upper atmosphere, but certain celestial events alter the magnitude of radiation that reaches the upper atmosphere. In the case of a solar eclipse, the moon directly shields a large portion of the Earth from solar radiation. This decreases both the temperature and ionization rate of the upper atmosphere, which in turn decreases the conductivity. A solar flare on the other hand increases the available ionizing energy, and consequently increases the conductivity of the ionosphere. Because the ionosphere is electrically coupled to the magnetosphere, changes in conductivity must necessarily affect the way that coupling occurs. In Chapters 1 and 3, we introduce some of the instrumen- tation used in observing magnetosphere-ionosphere coupling dynamics, as well as some of the difficulties associated with remote instrument operations in the high-latitude regions of Earth. Chapter 4 presents a case study of an Antarctic total solar eclipse, in which magnetic waves are observed from both northern and southern polar regions. The body of work in Chapter 5 suggests that large spatial scale variations in ionospheric conductivity related to solar eclipses are associated with geomagnetic substorms. All together, the research herein highlights the importance of considering ionospheric conductivity as a controlling parameter for magnetosphere-ionosphere coupling. / Doctor of Philosophy / Earth's upper atmosphere consists of an energetic and electromagnetically reactive plasma. This region plays an important role in over-the-horizon and satellite radio communications, and can impact human infrastructure. Activity in this region is influenced by plasma in space near Earth. This region is formed by interactions between energetic particles from the sun and Earth's magnetic field. It is occasionally the case that this near-Earth plasma is disturbed and rapidly moves into the upper atmosphere, resulting in brilliant auroral displays. One of the important factors that controls how this plasma and energy moves is the conductivity of the upper atmosphere region. This varies with latitude and season, but also changes more rapidly during special solar events. In the case of a solar eclipse, the moon directly shields a large portion of the Earth from solar radiation. This decreases both the temperature and ionization rate of the upper atmosphere, which in turn decreases conductivity. A solar flare on the other hand increases conductivity. In Chapters 2 and 3, we introduce some of the instruments used to observe the upper atmosphere plasma regions, as well as some of the difficulties associated with remote instrument operations in the high-latitude regions of Earth. Chapter 4 presents a case study of an Antarctic total solar eclipse, in which magnetic waves are observed from both northern and southern polar regions. Chapter 5 suggests that solar eclipses are associated with the previously mentioned plasma transfers from near-Earth space into the atmosphere. All together, the research herein highlights the importance of considering conductivity as a controlling parameter for energy and plasma transfer in the two regions.

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Neutron stars are surrounded by dense magnetospheres with nontrivial magnetic field structure. They are sources of multi-band emission from radio waves to very high energy gamma-rays. Pulsar wind nebulae observations also show that a large number of e^± pairs flow from the neutron star, which are produced in the magnetosphere. The structure of the magnetosphere, the mechanism of pair production and particle acceleration in the magnetosphere, and how magnetic energy is converted to kinetic energy is a complex problem that only recently has started to be addressed fully from first principles. In this dissertation I describe how I developed a numerical code tailored to study this problem. A detailed description of the code and method is given, then it is used to study the pair discharge mechanism in the magnetosphere of rotating neutron stars whose rotating axis is aligned with the magnetic axis. It was found that to form the an active magnetosphere it is necessary to have pair creation all the way towards the light cylinder. In the dissertation I classify the pulsars into two classes, and describe their differences. The magnetospheres of magnetars are believed to be different from ordinary pulsars, in that they are sustained not by the rotation of the star, but by a twist launched from the stellar surface due to some sudden breakdown of the crust. I apply the same numerical tool to study the particle acceleration and pair creation mechanism in the twisted magnetosphere of the magnetar, showing where the gap is, and how the magnetosphere evolves over time. The magnetic twist was found to live much longer than the Alfvén time of the system, and slowly dissipates through developing a cavity in the inner magnetosphere. This not only explains the long term evolution of the magnetar lightcurve after an outburst, but also explains the observed evolution hotspots on the stellar surface.