A telluric current (from Latin tellūs, "earth") is an electric 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.
Telluric currents are phenomena observed in the Earth's crust and mantle. In September 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. These currents are known to have diurnal characteristics wherein the general direction of flow is towards the sun.  Telluric currents will move between each half of the terrestrial globe at all times. Telluric currents move equator-ward (daytime) and pole-ward (nighttime).
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.
In industrial prospecting activity that uses the telluric current method, electrodes are properly located on the ground to sense the voltage difference between locations caused by the oscillatory telluric currents.  It is recognized that a low frequency window (LFW) exists when telluric currents pass through the earth's substrata. In the frequencies of the LFW, the earth acts as a conductor.
The main plot of the novel Foucault's Pendulum by Umberto Eco revolves around search of the Ombilicus Mundi (Latin: The Navel of the World), the mystic Center of The Earth which is supposed to be a certain point from where a person could control the energies and shapes of the earth thus reforming it at will. The novel takes this even further by suggesting that monuments like the Eiffel Tower are nothing more than giant antennae to catalyze these energies.
Telluric currents – along what are effectively ley lines – are discovered to be a means of mysterious communication in Thomas Pynchon's Mason and Dixon and are associated with the book's Chinese-Jesuit sub plot. As with Eco, cited above, Pynchon also reflects upon hollow earth theories in this work.
- ↑ , D. L. Hings, Telluric current responsive device having spaced conductors for positioning adjacent the Earth's surface
- ↑ Jahr, Emil, " Method of utilizing electrical earth currents".
- ↑ Dobrin, "Introduction to Geophysical Prospecting", McGraw Hill (3rd Ed. 1976) pg. 592.
- ↑ , C. L. Kober, Passive geophysical prospection system based upon the detection of the vertical electric field component of telluric currents and method therefore
- ↑ Burrell et al., "Pulse Propagation in Lossy Media Using the Low Frequency Window for Video Pulsed Radar Application", Proceedings of the IEEE, Vol. 67, No. 7, July 1979, pgs. 981-990.
Further reading Edit
- "Telluric current" A Dictionary of Earth Sciences. Ed. Ailsa Allaby and Michael Allaby. Oxford University Press, 1999.
- "The Earth's Electrical Environment". US National Academies Press, 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.
- Lamont, J. V., "Der Erdstrom und der Zusammen desselben mit dem Erdmagnetismus". Leopold-Voss-Verlag, Leipzig und Muenchen, 1862.
- 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 by 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.
- "Electrical Conductivity : Models of the Crust and Mantle". [PDF]
- MTNet, Scientists engaged in the study of the Earth using electromagnetic methods, principally the magnetotelluric technique (magnetotellurics).
- Gummow, R. A., "Telluric and Ocean Current Effects on Buried Pipeline and their Cathodic Protection Systems". CORRENG Consulting Service, Inc. December 03, 2002.
- Sinha, M. C., et al., "Applications of 3-Dimensional Electromagnetic Induction by Sources in the Ocean, ISO-3D". RTD Project, MAST III (Area C: Marine Technology). MAS3-CT97-0120