Interpretation of Long Wavelength Magnetic Anomalies

  • Paolo Gasparini
  • Marta S. M. Mantovani
  • Wladimir Shukowsky
Part of the Ettore Majorana International Science Series book series (EMISS, volume 11)


The Earth’s magnetic field (emf) measured at or above the Earth’s surface has two main components of internal origin: a primary (or main) field which is originated in the outer core and appears as large scale features at the Earth’s surface, and a secondary field which is due to both induced and remanent magnetization of high susceptibility ferrimagnetic minerals occurring in crustal rocks. The latter field is much weaker than the main field and it is locally variable according to the nature of the underlying crustal rocks. These two components of the emf appear clearly in a power spectrum analysis of the emf intensity along a world encircling profile (Alldredge et al., 1963). The energy of the spectrum is concentrated at wavelengths greater than about 2,000 km and smaller than 400–500 km (Fig.1). In the representation of the emf as an infinite series of spherical harmonic functions, the main field therefore is described by the harmonics up to order and degree about (13, 13) and the field of crustal origin by harmonics higher than (40, 40).


Curie Temperature Lower Crust Magnetic Anomaly Secular Variation Main Field 
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Copyright information

© Plenum Press, New York 1981

Authors and Affiliations

  • Paolo Gasparini
    • 1
    • 2
  • Marta S. M. Mantovani
    • 3
  • Wladimir Shukowsky
    • 3
  1. 1.Istituto di Geologia e GeofisicaUniversità di NapoliItaly
  2. 2.Osservatorio VesuvianoNapoliItaly
  3. 3.Instituto Astronomico e GeofisicoUniversidade de Sao PauloBrazil

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