Reference Work Entry

Geophysics

Part of the series Encyclopedia of Earth Science pp 517-522

Geomagnetic field analysis

  • Joseph C. Cain

The geomagnetic field observed about the Earth is the vector sum of several different components:

  • The main field, which is generated by electrical currents in the liquid core of the Earth and possibly by leakage currents into the deep mantle

  • The crustal or anomaly field, which results from direct magnetization of permeable material in the outer layers from the present main field, as well as remanent magnetization from ancient fields

  • The external field, produced by electrical currents in the ionosphere and magnetosphere, and modulated by the solar wind and the interplanetary field

  • The induced field, from electrical currents in the oceans and the conducting layers of the crust and mantle produced by flux changes from the external field, and possibly by changes in the core field.

The analysis of data must include consideration of all of these fields. Prior to satellite surveys, there was generally no distinction made between such sources. The word “geomagnetic” then meant the “regional” or ma ...

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