Low frequency geomagnetic fluctuations (.04 to 25 Hz) on land and on the floor of Monterey Bay
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Authors
McDevitt, Gerald R.
Homan, B. Bert
Subjects
low frequency geomagnetic measurements
geomagnetic fluctuations in an ocean environment
geomagnetic fluctuations in an ocean environment
Advisors
Heinz, O.
Date of Issue
1980-06
Date
June 1980
Publisher
Monterey, California. Naval Postgraduate School
Language
en_US
Abstract
A coil antenna consisting of approximately 6000 turns
of copper wire was utilized to measure the horizontal component
of fluctuations of the earth's magnetic field on the
floor of Monterey Bay in water depth of approximately 50
meters. The results indicate that the power spectral density
of the fluctuations varies from 10nT²/Hz at 0.04 Hz to
10ˉ⁶nT²/Hz at 25 Hz, a monotonic decrease of about 6 dB/
octave, except in the 8-20 Hz region where the Schumann
resonances occur. While the sensitivity of the equipment
was insufficient to measure the vertical component of the
fluctuation we can put an upper limit of 10ˉ³nT²/Hz at 1 Hz
and 10ˉ⁶(nT)²/Hz at 10 Hz on the magnitude of this component.
The same sensor was also used to measure various components
of the field fluctuations at a remote land' site
(Chew's Ridge). In the frequency range observed the general
shape of the spectra was similar to those obtained at
sea. However, a strong azimuthal variation at certain
frequencies was noted in the land data. The possibility
that these directional signals are of man made origin
cannot be excluded at this time.
Type
Thesis
Description
Series/Report No
Department
Physics and Chemistry
Organization
Naval Postgraduate School (U.S.)
Identifiers
NPS Report Number
Sponsors
Funder
Format
Citation
Distribution Statement
Approved for public release; distribution is unlimited.
Rights
This publication is a work of the U.S. Government as defined in Title 17, United States Code, Section 101. Copyright protection is not available for this work in the United States.