Telluric currents

Telluric currents are the currents that are responsible for the generation of earth's magnetic field. Also the help the earth to bound onto the solar path around the sun.

1. TELLURIC CURRENTS BY R. J. S. KASYAP, D. A. YASASKAR

2. CONTENTS INCEPTION HOW ARE THEY FORMED HISTORY RECENT HOW IS THE NATURE INVOLVED? HOW IS THE MAN INVOLVED? APPLICATIONS CONCLUSION 2

3. HAVE YOU EVER QUESTIONED SOMEONE OR YOURSELF “WHY WE ARE STICKING ON TO THE EARTH?” INCEPTION/ DESCRIPTION 3 If not, you are gonna sleep satisfactorily tonight if you would come across this presentation. First of all, how many types of currents are available in our daily life? There is another kind of current that is available and that is the TELLURIC CURRENT . This is not a new invention. This was actually identified in the month of September of the year 1862 . A Telluric current (from Latin  tellūs , "earth"), or Earth current , 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

4. HOW ARE THEY FORMED? 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). Including minor processes, there are at least 32 different mechanisms which cause telluric currents .The strongest are primarily geomagnetically induced currents, which are 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. The electric potential on the Earth's surface can be measured at different points, enabling the calculation of the magnitudes and directions of the telluric currents and hence the Earth's conductance. These currents are known to have diurnal characteristics wherein the general direction of flow is towards the sun .Telluric currents continuously move between the sunlit and shadowed sides of the earth, toward the equator on the side of the earth facing the sun (that is, during the day), and toward the poles on the night side of the planet . 4

5. History Planetary-scale distribution of Telluric currents according to Gish (1936a, 1936b) at 1800 GMT 5

6. Recent 6 (a) External Sq current systems averaged worldwide for D months (northern winter; top left), E months (equinox, top right), and J months (northern summer, bottom left), and their yearly average (bottom right). The current intensity between two consecutive lines is 25 × 103 A; the thick solid curves indicate the zero-intensity lines. The numbers near the central dots are the total current intensities of these vortices in units of 10 A. (b) Internal Sq current systems averaged worldwide for D months (top left), E months (top right), and J months (bottom left), and their yearly average (bottom right). Notice the disagreement with the previous figure; the rotational senses of the vortices are opposite. This figure adapted from Matsushita (1967).

7. HOW IS THE NATURE INVOLVED? Shallow :- Effects on shallow telluric currents (generally shorter period) can be found whenever a mineral has some remarkably different electrical conductivity compared with that of the surrounding materials. This gives rise to a localized conductivity anomaly that can be studied by means of a dense network of recording instruments. Shallow currents have also been reported in several sedimentary basins, such as in the Seine Basin and in the northern German anomaly .Shallow telluric currents are responsible for a component of the coast effect or magnetic signals, where the geometrical orientation of the magnetic variations at higher frequencies are correlated with the shape of the coast. The coast effect has been reviewed by Fischer (1979), Parkinson and Jones (1979), and Gregory and Lanzerotti (1979b). Deep :- The best recognized, by seismic waves, underground discontinuity has no obvious correspondence in geo-electromagnetic phenomena. Chapman and Pollack (1977) derived the lithosphere results by determining the depth at which both continental and oceanic geotherms intersect the mantle solidus. They showed this to be a consistent estimator of the depth to the top of the seismic low-velocity channel or of the thickness of the high-velocity lid overlying the channel. They identified the lid as synonymous with the lithosphere. 7

8. HOW IS THE MAN INVOLVED? The natural telluric current environment can significantly affect man-made systems. Conversely, human technology can "pollute" the natural telluric current environment. The mechanisms by which these interactions occur, as well as their modeling, are far from being understood satisfactorily and comprehensively. Geophysicists have often viewed such interactions as an unwanted, unnatural nuisance. The major factors involved are, Communication cables Power lines Pipelines Railways Corrosion 8

9. Applications Prospecting of Underground Structures Detection of Electromagnetic Signals from Space Deep-Earth Studies Tidal Phenomena and Water Flows Earth's Astronomical Motion Earthquakes, Volcanoes, and Geodynamics Communications Biological Effects 9

10. C oncl usion 10

11. For the valuable time

12. A ny qu eries? 12