GPS total electron content techniques for observing the structure and dynamics of the high latitude ionosphere

Abstract

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.