globalchange  > 气候变化与战略
DOI: 10.1016/j.epsl.2020.116507
论文题名:
Response of Earth's magnetic field to large lower mantle heterogeneity
作者: Sahoo S.; Sreenivasan B.
刊名: Earth and Planetary Science Letters
ISSN: 0012821X
出版年: 2020
卷: 549
语种: 英语
中文关键词: core flows ; core–mantle interaction ; geomagnetic field
英文关键词: Buoyancy ; Geomagnetism ; Heat convection ; Magnetic flux ; Shear flow ; Shear waves ; Wave propagation ; Boundary heat flux ; Cylindrical annulus ; Earth's magnetic field ; Geomagnetic fields ; Lateral variations ; Magnetic flux concentration ; Relative instability ; Shear wave velocity ; Heat flux ; core (planetary) ; experiment ; geomagnetic field ; geostrophic flow ; heat flux ; heterogeneity ; lower mantle ; mantle convection ; spatial variation ; Canada
英文摘要: A simplified two-fold pattern of convection in the Earth's core is often used to explain the non-axisymmetric magnetic flux concentrations in the present day geomagnetic field. For large lateral variations in the lower mantle heat flux, however, a substantial east–west dichotomy in core convection may be expected. This study examines the effect of a large lateral variation in heat flux at the outer boundary in cylindrical annulus experiments that achieve approximate geostrophy of the convection as well as in rapidly rotating spherical shell simulations. In either geometry, the imposed boundary heat flux is derived from the seismic shear wave velocity in the lowermost mantle. The pattern of large-scale convection in the simulations closely follows that in the annulus experiments, which suggests that the lateral buoyancy at the equator essentially determines the structure of core convection. In particular, the location of a coherent downwelling that forms beneath Canada in mildly driven convection entirely switches over to the Siberian region in strongly driven states. Spherical dynamo models in turn show that this eastward migration of convection causes the relative instability or even the disappearance of the high-latitude magnetic flux in the Western hemisphere. Finally, large radial buoyancy causes homogenization of convection, which may place an upper bound for the Rayleigh number in the core. © 2020 Elsevier B.V.
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资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/165250
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作者单位: Department of Applied Geophysics, Indian Institute of Technology (ISM), Dhanbad, 826004, India; Centre for Earth Sciences, Indian Institute of Science, Bangalore, 560012, India

Recommended Citation:
Sahoo S.,Sreenivasan B.. Response of Earth's magnetic field to large lower mantle heterogeneity[J]. Earth and Planetary Science Letters,2020-01-01,549
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