Ambient and target magnetic fields measured in Bedford Basin

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Authors
  1. Daya, Z.A.
  2. Fontaine, F.
  3. Le Puil, M.
Corporate Authors
Defence R&D Canada - Atlantic, Dartmouth NS (CAN)
Abstract
Induction coil measurements of the rate of change of the magnetic field were obtained at ocean floor depths of about 15 m for a duration of approximately 8 hours. The 3 vector components of the magnetic field were obtained by integrating the data over time. Each component of the magnetic field was decomposed into trend and fluctuations by filtering in the frequency domain. Our results show that the trends of each component has long time correlations (~ 1 hour) but that the fluctuations are uncorrelated. When the fluctuations are scaled by their standard deviations, we find that both the fluctuations in the individual components and those for the magnitude of the magnetic field share a common probability distribution function. This distribution is approximated by a stretched exponential (i.e. ~ e -|η|γ) with γ ≈ 1.5 for ≤ 3 rms deviations. The frequency power spectra of the components and magnitude of the magnetic field measurements have ƒδ power-law scaling with δ ~ -2 for frequency 0.001 ≤_ ƒ ≤ 1.0 Hz. A magnetic target at close range was observed in the induction coil data. We coarsely modeled it as a point dipole to extract the speed, range and heading.

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Report Number
DRDC-ATLANTIC-TM-2007-308 — Technical Memorandum
Date of publication
01 May 2008
Number of Pages
44
DSTKIM No
CA032168
CANDIS No
531290
Format(s):
CD ROM

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