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Global Assessment of Precipitation of Radiation Belt Electrons by Electromagnetic Waves from Lightning

出版	Stanford University, 2011
ISBN	STANFORD:fv996mh8063
URL	http://books.google.com.hk/books?id=s_hTNIOzJPkC&hl=&source=gbs_api
EBook	SAMPLE

註釋Lightning discharges are well known sources of electromagnetic radiation in the frequency range of a few Hz to many MHz, with the most intense radiation typically being in the range of 5--10 kHz. Electromagnetic waves originating in lightning discharges often propagate through the most densely ionized regions of the Earth's atmosphere and populate the radiation belts. High-energy electrons in this region constitute a hazard to the increasing number of scientific and commercial spacecraft that orbit the Earth, and quantitative understanding of this radiation and its sources and losses are thus important. Electromagnetic whistler waves injected into the radiation belts by lightning discharges can pitch-angle scatter the energetic electrons and cause them to precipitate out of their stably trapped radiation belt orbits and onto the dense upper atmosphere of the Earth. This dissertation examines the detection of lighting-induced energetic electron precipitation via long-term analysis of in-situ observations of drift loss cone fluxes (i.e., fluxes destined to be precipitated over the South Atlantic Anomaly within ~2 hours). The primary measurement tool used is an energetic electron detector (IDP) on board the DEMETER satellite---a French micro-satellite in a sun-synchronous low Earth orbit. Energetic electron flux data are analyzed alongside ground-based lightning data recorded by the National Lightning Detection Network (NLDN) to determine the relationship between drift loss cone fluxes and lightning. While lighting-induced electron precipitation events occur globally, the best region for making in-situ observations of fluctuations in drift loss cone fluxes is over the continental United States. Measurements of VLF wave activity in the typical frequency range of lightning-generated whistler waves (5--10 kHz) on DEMETER show a substantial increase of electromagnetic wave power over the United States, particularly during the northern summer months when lightning activity is at its highest. Analysis of particle precipitation data on the DEMETER spacecraft over a three-year period shows that energetic electron fluxes in the drift loss cone exhibit a seasonal dependence consistent with lightning-induced electron precipitation (LEP) being an important source of loss of such energetic radiation. Over the United States, energetic electron fluxes in the slot region (2