ERTH 2415 Lecture Notes - Lecture 12: Outer Core, Faraday'S Law Of Induction, Electromagnetic Induction
14 Mar 2019
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Document Summary
Magnetic fields induce current, current induces magnetic field. Variations in earth"s magnetic field induce electrical ( telluric") currents o o. Recorded for a few hours to a few days o. Used to estimate the electrical conductivity in the subsurface (regional scale) Artificial varying magnetic field induces currents in subsurface ore bodies. These currents generate a magnetic field recorded at the surface or from the air. Estimate the depth, shape and electrical conductivity of subsurface ore bodies o. Metallic ore bodies are more conductive than surrounding rocks. Extreme variations of the earth"s magnetic field can have significant impact on technological systems. Geomagnetic effects have been observed for 150 years after disturbances on the telegraph occurred. Magnetometers at the surface of the earth record superposition signals from internal (earths core) and external (ionosphere, magnetosphere) geomagnetic fields. Due to movement of liquid iron in outer core. Heat transfer by convection at the outer-inner core boundary.
