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Interactions between whistler-mode waves and energetic electrons in the coupled system formed by the magnetosphere,ionosphere and atmosphere
Institution:1. Dairy Science Group, School of Life and Environmental Science, Faculty of Science, The University of Sydney, Camden, NSW 2570, Australia;2. Animal Welfare Science Centre, Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, Parkville, Vic 3010, Australia;1. School of the Environment, Geography and Geological Sciences, University of Portsmouth, Burnaby Building, Burnaby Road, Portsmouth, PO13QL, United Kingdom;2. Earth Science Department, Natural History Museum, Cromwell Road, London, SW75BD, United Kingdom;3. Bullard Laboratories, Department of Earth Sciences, University of Cambridge, Madingley Rise, Madingley Road, Cambridge CB3 0EZ, United Kingdom;1. Department of Cardiovascular Biology and Medicine, Juntendo University Graduate School of Medicine, Tokyo, Japan;2. Department of Radiology, Juntendo University Graduate School of Medicine, Tokyo, Japan;3. Japan Agency for Medical Research and Development-Core Research for Evolutionary Medical Science and Technology (AMED-CREST), Japan Agency for Medical Research and Development, Tokyo, Japan;1. Departemnt of Agricultural Engineering, SNS College of Technology, Coimbatore 641035, India;2. Departemnt of Civil Engineering, SONA College of Technology, Salem 636005, India;3. Departemnt of Civil Engineering, KPR Institute of Engineering and Technology, Coimbatore 641407, India
Abstract:The physical mechanism of a cyclotron resonance interaction between trapped energetic electrons and whistler-mode waves in the magnetosphere is discussed. Not only do the electrons have their pitch angles reduced in this interaction, so that they may be precipitated into the upper atmosphere, but also the waves can be amplified. Such a flux of precipitating electrons can, either by direct ionisation or via bremsstrahlung radiation, cause a pimple to be produced on the bottom of the ionosphere. That can significantly modify the amplitude and/or phase of very low frequency radio signals propagating in the Earth-ionosphere waveguide. Various experimental observations that demonstrate the reality of such effects are reviewed. The conditions necessary for a positive feedback situation are discussed, and some evidence for its existence assessed.
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