Browsing by Author "Watson, Chris"

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    GPS total electron content techniques for observing the structure and dynamics of the high latitude ionosphere
    (University of New Brunswick, 2015) Watson, Chris; Jayachandran, P.T. Thayyil
    The solar wind, magnetosphere and ionosphere (SW-M-I) constitute a highly coupled system, where solar wind energy drives dynamic processes of the magnetospheric cavity and embedded ionosphere. The high latitude ionosphere has an inherently complex structure and dynamic behavior due to direct coupling to the solar wind and outer magnetosphere. Energy and charged particles deposited in the high latitude ionosphere via SW-M-I coupling processes generate ionization structures with variable spatial scales and dynamic behavior. Characteristics of ionization structures, such as their source, generation mechanisms, and evolution, are not well understood, largely due to past inadequacies in observational capabilities at high latitudes. From a physics perspective, the observation of high latitude ionospheric processes and structures is a proven technique for studying physical processes in the magnetosphere and solar wind. From an industrial and societal perspective, the dynamic high latitude ionosphere is potentially problematic due to significant impacts on electromagnetic signals used for navigation and communication. Recent installation of high data rate Global Positioning System (GPS) receivers of the Canadian High Arctic Ionospheric Network (CHAIN) has provided new, high resolution observations of the high latitude ionosphere. This thesis uses a statistical study and case studies to investigate the characteristics and source regions of ionospheric total electron content (TEC) variations observed by CHAIN GPS receivers. In the statistical study, occurrence rate, amplitude, and frequency of TEC variations were examined, in order to investigate the dependence of these characteristics on magnetic local time, latitude, and solar wind conditions. In three case studies, variations in TEC resulting from ultra-low frequency (ULF) waves in Earth’s geomagnetic field were observed. It is shown that GPS TEC has a significant response to various ULF wave classifications and intensities, and is a potentially valuable tool for high resolution study of ULF activity and the associated ionospheric response.
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    Survey of magnetic pulsations at the geosynchronous orbit
    (University of New Brunswick, 2008) Watson, Chris
    Magnetic pulsations are Ultra Low Frequency (ULF) electromagnetic waves and are considered to be one of the modes for transfer of energy and momentum from the solar wind to the magnetosphere and different plasma regimes within the magnetosphere. Magnetic pulsations are usually identified using ground based magnetometer measurements and are classified into different categories. In this study, we have used ten years of GOES satellite geo-synchronous magnetic field measurements to identify and characterize magnetic pulsations. Our analysis resulted in 962 clear pulsation events in Pc5, Pi2 and Pc4 bands. Two satellite locations were used in the study, giving a comparison of pulsation events at two different local times. Upon finding a pulsation, a time-frequency spectral analysis was employed to determine the pulsation frequency. Pulsations were found to occur most frequently in the late morning to evening sector, with their time duration following a power law distribution. Frequencies in the 5 to 8 mHz band were the most common, however a broad range of frequencies were found. A possible frequency dependence on magnetic field inclination was found, although more study is needed to be conclusive.