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Maritime Electromagnetism and DRDC Signature Management Research

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Technical Report

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Defence R and D Canada Atlantic Dartmouth, NS

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The broad field of electromagnetic activity in maritime environments is selectively reviewed from the perspective of scientific signature management. The physical origins and characteristics of naturally occurring electromagnetism i.e. ambient electromagnetic fields in the oceans are described. In particular, the sources or physical processes generating the fields, their magnitudes and the relevant time scales are noted. The ambient fields include the Earths geomagnetic field, electromagnetic fields arising from the Earth-Ionosphere coupling and induced fields from oceanic flows. Localized electromagnetic signatures i.e. those emanating from naval platforms are reviewed. The signature strengths, their spatial and temporal extent, their origin and the representative physical models are discussed. Platform signatures include electromagnetic effects stemming from corrosion, permanent and induced magnetization of ferromagnetic components, and electromagnetic fields propagating from coastal settlements. Magnetic and electric signature management principles such as degaussing and active shaft grounding, respectively, are described. Defence Research and Development Canada DRDC contributions and present-day competencies in electromagnetic signatures are discussed. Possible directions for DRDC electromagnetic signature management are suggested.

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