Magnetic Signature of Surface Waves Measured in a Laboratory Experiment

John A. Kluge, Alexander V. Soloviev, Cayla W. Dean, Bradley Nelson, William E. Avera, George Valdes, Brian K. Haus

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

Seawater moving in Earth's magnetic field causes secondary magnetic field fluctuations, which creates a magnetic signature. A laboratory experiment was conducted at the SUrge STructure Atmosphere INteraction (SUSTAIN) facility, to measure the magnetic signature of surface waves. We used a differential method, placing two Geometrics G-824 magnetometers at several locations on the outer tank walls, separated horizontally by one-half wavelength. This method effectively suppressed extraneous magnetic distortions, which both sensors should see simultaneously, and possible tank vibrations while doubling the magnetic signal of surface waves. The wave parameters used in this experiment were 2 m long waves with a 0.56 Hz frequency and 0.1 m amplitude. Three Senix ultrasonic sensors positioned on the top of the tank were used to measure wave elevation. Freshwater, salt water, and empty tank experiments were conducted to measure the magnetic difference between fresh and salt water. Additionally, the empty tank tests indicated that noise levels from the SUSTAIN facility are much smaller than the useful (differential) signal recorded in our fresh and salt water experiments. Spectral analysis of the magnetic signal shows the main peak at the wave frequency of 0.56 Hz and less pronounced higher frequency harmonics, which are due to non-linearity of shallow water surface waves. Our results suggest that the magnetic signature generated by surface waves were an order of magnitude larger than predicted by the traditional model (Podney 1975). Based on theoretical calculations, the discrepancy may come from the difference of magnetic permeability in water and air that is not accounted in the traditional model.

Original languageEnglish (US)
Title of host publicationOCEANS 2018 MTS/IEEE Charleston, OCEAN 2018
PublisherInstitute of Electrical and Electronics Engineers Inc.
ISBN (Electronic)9781538648148
DOIs
StatePublished - Jan 7 2019
EventOCEANS 2018 MTS/IEEE Charleston, OCEANS 2018 - Charleston, United States
Duration: Oct 22 2018Oct 25 2018

Publication series

NameOCEANS 2018 MTS/IEEE Charleston, OCEAN 2018

Conference

ConferenceOCEANS 2018 MTS/IEEE Charleston, OCEANS 2018
CountryUnited States
CityCharleston
Period10/22/1810/25/18

Keywords

  • Electromagnetism
  • Laboratory experiment
  • Surface waves

ASJC Scopus subject areas

  • Renewable Energy, Sustainability and the Environment
  • Oceanography

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