Source Variation and Ground Accessibility of Magnetospheric Mid-latitude ELF/VLF Chorus and Hiss

Download or read book Source Variation and Ground Accessibility of Magnetospheric Mid-latitude ELF/VLF Chorus and Hiss written by Daniel Irving Golden and published by Stanford University. This book was released on 2011 with total page 192 pages. Available in PDF, EPUB and Kindle. Book excerpt: The distribution of relativistic electrons that form the Earth's radiation belts is extremely variable, with the trapped flux changing by several orders of magnitude on timescales of a few hours to days. These energetic particles pose a significant hazard to satellites and astronauts in the near-Earth space environment. The dynamic evolution of the radiation belts is believed to be controlled in large part by two separate but related classes of naturally occurring plasma waves: extremely low frequency/very low frequency (ELF/VLF) chorus and hiss. This dissertation explores characteristics of chorus and hiss observed at Palmer Station, Antarctica with the goal of improving our ability to differentiate between variations in emission generation and the effects of emissions' propagation to the ground. Results are presented from a two-part study, consisting of both observations and modeling, which explores the manner in which the plasmapause affects the propagation of chorus from its magnetospheric source to the ground. Results indicate that the observed chorus propagates in a non-ducted mode, which is contrary to a long-standing belief that guiding structures are necessary for chorus to propagate to the ground. This newly-explored mode of ground propagation indicates that ground stations may be able to observe a larger portion of waves than previously thought and provides for a more accurate interpretation of ground-observed waves and their influence on energetic particle distributions. Following this, an automated system of detecting chorus and hiss in broadband ELF/VLF data using neural networks is discussed. Results of running the automated detector on ten years of data are discussed including diurnal, seasonal and solar cyclical variations of emissions.