Abstract
We propose that one of the main causes of the secular variation of the geomagnetic field is length-of-day (LOD) variation, namely, the variation of the rotation velocity of the mantle. We developed an analytical model, in which fluctuations of the rotation velocity of the mantle induces flow in the outer core through topographic coupling at the core-mantle boundary (CMB). The flow in turn bends the toroidal field to produce a poloidal field. Secular variation of the sectorial components of the geomagnetic field, from decadal to millennial time scale, is explained very well by our model. By comparing our theory with observations, we inferred important properties of the outer core and the mantle: the strength and the direction of the toroidal field, the dispersion relation of the slow magnetohydrodynamic oscillation, and the topography of the CMB.
| Original language | English |
|---|---|
| Pages (from-to) | 73-78 |
| Number of pages | 6 |
| Journal | Proceedings of the Japan Academy, Series B |
| Volume | 69 |
| Issue number | 4 |
| DOIs | |
| Publication status | Published - Jan 1 1993 |
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All Science Journal Classification (ASJC) codes
- Agricultural and Biological Sciences(all)
- Physics and Astronomy(all)
Cite this
15. Geomagnetic Secular Variations are caused by Length-of-day Fluctuations. / Yoshida, Shigeo; Hamano, Yozo.
In: Proceedings of the Japan Academy, Series B, Vol. 69, No. 4, 01.01.1993, p. 73-78.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - 15. Geomagnetic Secular Variations are caused by Length-of-day Fluctuations
AU - Yoshida, Shigeo
AU - Hamano, Yozo
PY - 1993/1/1
Y1 - 1993/1/1
N2 - We propose that one of the main causes of the secular variation of the geomagnetic field is length-of-day (LOD) variation, namely, the variation of the rotation velocity of the mantle. We developed an analytical model, in which fluctuations of the rotation velocity of the mantle induces flow in the outer core through topographic coupling at the core-mantle boundary (CMB). The flow in turn bends the toroidal field to produce a poloidal field. Secular variation of the sectorial components of the geomagnetic field, from decadal to millennial time scale, is explained very well by our model. By comparing our theory with observations, we inferred important properties of the outer core and the mantle: the strength and the direction of the toroidal field, the dispersion relation of the slow magnetohydrodynamic oscillation, and the topography of the CMB.
AB - We propose that one of the main causes of the secular variation of the geomagnetic field is length-of-day (LOD) variation, namely, the variation of the rotation velocity of the mantle. We developed an analytical model, in which fluctuations of the rotation velocity of the mantle induces flow in the outer core through topographic coupling at the core-mantle boundary (CMB). The flow in turn bends the toroidal field to produce a poloidal field. Secular variation of the sectorial components of the geomagnetic field, from decadal to millennial time scale, is explained very well by our model. By comparing our theory with observations, we inferred important properties of the outer core and the mantle: the strength and the direction of the toroidal field, the dispersion relation of the slow magnetohydrodynamic oscillation, and the topography of the CMB.
UR - http://www.scopus.com/inward/record.url?scp=85008068261&partnerID=8YFLogxK
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U2 - 10.2183/pjab.69.73
DO - 10.2183/pjab.69.73
M3 - Article
AN - SCOPUS:85008068261
VL - 69
SP - 73
EP - 78
JO - Proceedings of the Japan Academy Series B: Physical and Biological Sciences
JF - Proceedings of the Japan Academy Series B: Physical and Biological Sciences
SN - 0386-2208
IS - 4
ER -