The southern hemisphere has always been the neglected twin in the field ot geophysical research. The reasons for this are certainly not in the realm of science but in the history of man and his development in the northern half of the globe. Geophysically, however, our southern half provides a wealth of interesting problems and anomalies. Roederer (1966) explains the use of this word 'anomaly' by showing what some of the oddities of the southern hemisphere are, and by contrasting them with the corresponding regions of the earth across the equator. The principal feature is of course the geomagnetic surface field strength minimum at a point in the South Atlantic ocean very near the coast of Brazil. Intro., p. 1.

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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. / 2031-01-01

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Physics, 1980. / Vita. / Bibliography: leaves 140-156. / by Ralph L. McNutt, Jr. / Ph.D.

Intervals of Steady Magnetospheric Convection (SMC) are loosely defined as times when convection in the magnetosphere as a whole is enhanced and there are no substorm signatures. A lack of substorm signatures implies that the large scale structure of the magnetotail is maintained. There have been several quantitative methods developed to detect SMC events. None of these methods are based on observations of convection. The Super Dual Auroral Radar Network (SuperDARN) is a useful tool for studying SMC, because it gives a direct measurement of convection on a global scale. Previous SMC selection methods have made use of ground based magnetometer responses to auroral currents in the atmosphere. These methods resulted in a strong seasonal dependence in SMC occurrence due to seasonal changes in ionospheric conductivity. A new SMC selection criterion was developed to improve upon the previous criteria. This new method identifies all the events found using currently accepted methods plus additional intervals that reduce the seasonal dependence in SMC occurrence. SuperDARN was used to evaluate the old and new selection methods. According to SuperDARN convection observations, the new SMC selection criterion largely eliminated ionospheric conductivity effects. A conceptual model of the conductivity effects on the traditional SMC selection method was developed, and the occurrence of modelled SMC events agrees well with observations. Statistical studies have revealed that the additional SMC intervals have similar properties as events selected using traditional methods. Case studies confirmed the statistical results that SMCs selected by the new criterion have SMC properties. Both SMC events sets have a moderate solar wind driver, enhanced convection, and stable polar cap size. Statistical studies have also shown there was good SuperDARN data coverage during SMC, which is not typical of SuperDARN observations during enhanced and disturbed conditions in the magnetosphere. It is therefore shown to be an excellent tool with which to study SMC.

Intervals of Steady Magnetospheric Convection (SMC) are loosely defined as times when convection in the magnetosphere as a whole is enhanced and there are no substorm signatures. A lack of substorm signatures implies that the large scale structure of the magnetotail is maintained. There have been several quantitative methods developed to detect SMC events. None of these methods are based on observations of convection. The Super Dual Auroral Radar Network (SuperDARN) is a useful tool for studying SMC, because it gives a direct measurement of convection on a global scale. Previous SMC selection methods have made use of ground based magnetometer responses to auroral currents in the atmosphere. These methods resulted in a strong seasonal dependence in SMC occurrence due to seasonal changes in ionospheric conductivity. A new SMC selection criterion was developed to improve upon the previous criteria. This new method identifies all the events found using currently accepted methods plus additional intervals that reduce the seasonal dependence in SMC occurrence. SuperDARN was used to evaluate the old and new selection methods. According to SuperDARN convection observations, the new SMC selection criterion largely eliminated ionospheric conductivity effects. A conceptual model of the conductivity effects on the traditional SMC selection method was developed, and the occurrence of modelled SMC events agrees well with observations. Statistical studies have revealed that the additional SMC intervals have similar properties as events selected using traditional methods. Case studies confirmed the statistical results that SMCs selected by the new criterion have SMC properties. Both SMC events sets have a moderate solar wind driver, enhanced convection, and stable polar cap size. Statistical studies have also shown there was good SuperDARN data coverage during SMC, which is not typical of SuperDARN observations during enhanced and disturbed conditions in the magnetosphere. It is therefore shown to be an excellent tool with which to study SMC.

Thesis (Ph. D.)--University of Texas at Austin, 2003. / Vita. Includes bibliographical references. Available also from UMI Company.