Low frequency geomagnetic fluctuations (.04 to 25 Hz) on land and on the floor of Monterey Bay
McDevitt, Gerald R.
Homan, B. Bert
Moose, Paul H.
MetadataShow full item record
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.
RightsThis 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.
Showing items related by title, author, creator and subject.
Ames, Morgan P.; Vehslage, Louis McBane (Monterey, California. Naval Postgraduate School, 1981-12);Two coil antennas consisting of 5460 turns of copper wire were utilized to measure the vertical component and a horizontal component of the fluctuations of the geomagnetic field on the floor of Monterey Bay at a depth ...
Elster, Richard S. (Monterey, California. Naval Postgraduate School, 1972-05); NPS-55Ea72051AIn the comparison of military units or systems, many attributes including performance, might be measured. One general approach to determining 2which system is best involves forming a composite measure of the differentially ...
Richardson, Daniel J (Monterey, California. Naval Postgraduate School, 1997-06);Atmospheric optical turbulence induces phase fluctuations in a propagating electromagnetic wave. The resulting degradation in coherence limits the capability of any laser, target acquisition, or surveillance system. Past ...