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A nonlinear vacillating dynamo induced by an electrically heterogeneous mantle
Author(s) -
Chan Kit H.,
Zhang Keke,
Zou Jun,
Schubert Gerald
Publication year - 2001
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2001gl013453
Subject(s) - dynamo , dynamo theory , spherical shell , physics , magnetic field , mechanics , mantle (geology) , nonlinear system , amplitude , perfect conductor , classical mechanics , geophysics , shell (structure) , materials science , optics , quantum mechanics , composite material , scattering
This paper reports the first spherical numerical dynamo based on a three‐dimensional finite element method. We investigate a nonlinear dynamo in a turbulent electrically conducting fluid spherical shell of constant electric conductivity surrounded by an electrically heterogeneous mantle. Magnetic fields in the form of a three‐dimensional azimuthally traveling dynamo wave are generated by a prescribed time‐dependent α in the fluid shell. In the inner sphere, we assume that there is a solid electrical conductor with the same conductivity as that of the fluid shell. Equilibration of the generated magnetic fields is achieved by the nonlinear process of α‐quenching. We show for the first time that finite element methods can be effectively and efficiently employed to simulate three‐dimensional dynamos in spherical systems. We also show that an electrically heterogeneous mantle can modulate the core dynamo, leading to a vacillating dynamo whose amplitude depends upon the relative phases between the generated magnetic field and the heterogeneous mantle.