Telluric current

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This article is about the real electrical phenomenon. For the occult concept mentioned in fiction, see Foucault's Pendulum.

A telluric current (from Latin tellūs, "earth") is an electrical current which moves underground or through the sea. Telluric currents result from both natural causes and human activity, and the discrete currents interact in a complex pattern. The currents are extremely low frequency and travel over large areas at or near the surface of the Earth.

1 Description
2 Patents
3 References and further readings
4 See also
5 External links

[edit] Description

Telluric currents are phenomena observed in the Earth's crust and mantle. In September of 1862, an experiment to specifically address Earth currents was carried out in the Munich Alps (Lamont, 1862). The currents are primarily induced by changes in the outer part of the Earth's magnetic field, which are usually caused by interactions between the solar wind and the magnetosphere or solar radiation effects on the ionosphere. Tellurics also result from thunderstorms. Telluric currents flow in the surface layers of the earth. The electric potential on the Earth's surface can be measured at different points, enabling us to calculate the magnitudes and directions of the telluric currents and thence the Earth's conductance. Telluric currents will move between each half of the terrestrial globe at all times. Telluric currents move equator-ward (daytime) and pole-ward (nighttime).

The field varies in time and over the frequency range 0.001 to 5 Hz (Krasnogorskaja & Remizov, 1975). Electric potential gradients caused by telluric currents are of the order of 0.2 to 1000 volts per metre. (Krasnogorskaja and Remizov (1975); Vanjan (1975)). At any location, the current density is a direct function of the interhemispheric currents and their potential gradients. It has been estimated that telluric currents overall during twelve hours in one hemisphere are in range of 100 to 1000 amperes. This intensity of telluric currents is sufficient to drive the air movements that create atmospheric electricity, from the global fair weather charge accumulator to thunderstorm bases.

Both the telluric and magnetotelluric methods are used for exploring the structure beneath the Earth's surface (such as in industrial prospecting). For mineral exploration the targets are conductive ore bodies. Other uses include exploration of geothermal fields, petroleum reservoirs, fault zones, ground water, magma chambers, and plate tectonic boundaries. Telluric currents can be harnessed to produce a useful low voltage current by means of earth batteries. Such devices were used for telegraph systems in the United States as far back as 1859.

[edit] Patents

The United States Patent office has a division classification for geophysical electrical measuring devices of the telluric type [class 324/349] (including magneto-telluric types [class 324/350]). Other patents have utilized the earth's current outside this classification, also.

U.S. Patent 5043667 - J. D. Schofield, Method of magnetotelluric exploration using areal arrays
U.S. Patent 4945310 - J. R. Jackson, Passive geophysical survey method based upon the detection of the DC component of the vertical electrical potential of natural earth currents
U.S. Patent 4841250 - J. R. Jackson, Passive geophysical survey apparatus based upon the detection of the DC component of the vertical electrical potential of natural earth currents
U.S. Patent 4812766 - J. D. Klein,Telluric noise cancellation in induced polarization prospecting
U.S. Patent 4686475 - C. L. Kober, Passive geophysical prospection system based upon the detection of the vertical electric field component of telluric currents and method therefor
U.S. Patent 4473800 - B. N. Warner, Method for detecting magnetotelluric subsurface anomalies
U.S. Patent 4409551 - L. J. Norton, Telluric survey electrode
U.S. Patent 4339720 - M. O. Halverson, Telluric noise cancellation in induced polarization prospecting
U.S. Patent 4210869 - M. Goethe, Rotating telluric field measurements
U.S. Patent 3361957 - D. L. Hings, Telluric current responsive device having spaced conductors for positioning adjacent the Earth's surface
U.S. Patent 3,309,607 - S. H. Yungul, Method for the determination of direction of effective strike and dip from telluric potentials utilizing a T-spread quadruple electrode array
U.S. Patent 3,188,558 - S. H. Yungul, Telluric sounding method in which recording in the telluric field with time are converted into amplitude-versus-frequency spectra
U.S. Patent 2,586,667 - G. Kunetz, Method for the invvestigation of the ground
U.S. Patent 2,284,990 - M. Schlumberger, Method and apparatus for electrical prospecting
U.S. Patent 2,263,097 - J. A. Mmarchand, Geophysical prosecting
U.S. Patent 2,240,520 - M. Schlumberger, Method and apparatus for electrical underground prospecting
U.S. Patent 2,034,447 - M. Schlumberger, Method for electrically prospecting the undersoil
U.S. Patent 690151 - E. Jahr, Method of utilizing electrical earth currents

[edit] References and further readings

General

"Telluric current" A Dictionary of Earth Sciences. Ed. Ailsa Allaby and Michael Allaby. Oxford University Press, 1999.
"The Earth's Electrical Environment". Commission on Physical Sciences, Mathematics, and Applications, 1986.
- Louis J. Lanzerotti and Giovanni P. Gregori, "Telluric Currents: The Natural Environment and Interactions with Man-made Systems", Chapter 16.

Citations

Krasnogorska, N. V., and Remizov, V. P., "Pulsations of the earth's electric field", Physico-mathematical and biological problems of effects of electromagnetic fields and ionization of air, Moscow, Nauka, pp. 49-56, 1975(Russian).
Vanjan, L. P., "On the magnetospheric-ionospheric components of atmospheric electric field", Physico-mathematical and biological problems of electromagnetic field effects and air ionization. Proceedings of the All-Soviet Scientific Symposium, November 25-27, Yalta, Moscow, Nauka, Vol. 1, pp. 48-49, 1975. (Russian)
Lamont, J. V., "Der Erdstrom und der Zusammen desselben mit dem Erdmagnetismus". Leopold-Voss-Verlag, Leipzig und Muenchen, 1862.

Other

Wait, J.R., "On the relation between telluric currents and the earth’s magnetic field", Geophysics, 19, 281-289, 1954.
Gideon, D. N., A. T. Hopper, and R. E. Thompson, "Earth current effects on buried pipelines : analysis of observations of telluric gradients and their effects". Battelle Memorial Institute and the American Gas Association. New York, 1970.
Seeley, Robert L., Tippens, C. L., and Hoover, Donald B., "Circuitry of the U.S.G.S. telluric profiler". U.S. Geological Survey open-file report ; 87-332, Denver, Colo. : U.S. Dept. of the Interior, Geological Survey.
Berdichevskiĭ, Mark Naumovich, "Elektricheskaya razvedka metodom telluricheskikh tokov". Boston Spa, Yorkshire : National Lending Library for Science and Technology, 1963. LCCN 92140338 (Tr., "Electrical surveying by means of telluric currents"; Translation byt J.E.S. Bradley)
Hoover, Donald B., Pierce, H. A., and Merkel, D. C., "Telluric traverse and self potential data release in the vicinity of the Pinson Mine, Humboldt County, Nevada". U.S. Geological Survey open-file report; 86-341. U.S. Dept. of the Interior, Geological Survey, 1986.
Marti, B. A., "Telluric Effects on a Buried Pipeline".
Boteler, D.H., and W.H. Seager, "Telluric Currents: A Meeting of Theory and Observation"