Types of Liquid Core Motions Compatible With the Observed Geomagnetic Secular Variations of Several Hundred Years

  1. D. E. Smylie and
  2. Raymond Hide
  1. Takesi Yukutake and
  2. Yukiko Yokoyama

Published Online: 29 MAR 2013

DOI: 10.1029/GM046p0095

Structure and Dynamics of Earth's Deep Interior

Structure and Dynamics of Earth's Deep Interior

How to Cite

Yukutake, T. and Yokoyama, Y. (1988) Types of Liquid Core Motions Compatible With the Observed Geomagnetic Secular Variations of Several Hundred Years, in Structure and Dynamics of Earth's Deep Interior (eds D. E. Smylie and R. Hide), American Geophysical Union, Washington, D. C.. doi: 10.1029/GM046p0095

Author Information

  1. Earthquake Research Institute, University of Tokyo, Bunkyo-Ku, Tokyo, 113 Japan

Publication History

  1. Published Online: 29 MAR 2013
  2. Published Print: 1 JAN 1988

ISBN Information

Print ISBN: 9780875904504

Online ISBN: 9781118666562

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Keywords:

  • Earth—Core—Congresses;
  • Geodynamics—Congresses

Summary

The geomagnetic field is decomposed into standing and drifting parts of which the drifting field has a special spatial structure consisting of two types of fields, field of sectorial harmonic type (m, m) and that of the harmonics (m+1, m). When the dipole field and the toroidal field of (n=2, m=0) are assumed as primary fields, only three kinds of interaction are capable of inducing the observed poloidal fields, first interaction of toroidal motions with the dipole field, second interaction of poloidal motions with the toroidal field and third that of poloidal motions with the dipole field. Induced modes for these three interaction processes are computed and relative amplitudes of the induced poloidal modes are estimated to compare with the observed modes.

Among possible processes to explain the observed standing and drifting field, a proposed model is that the standing field is produced by laminar flows in a boundary layer near the core surface through interaction with the dipole field, whereas the drifting field of sectorial harmonics is generated by convection type motions of (m+1, m) mode, which is antisymmmetrie to the equator, interaction with both the toroidal and the dipole field in a deeper region of the core.