DOI: 10.1016/j.epsl.2019.115888
论文题名: Ohmic dissipation in the Earth's outer core resulting from the free inner core nutation
作者: Lin Y. ; Ogilvie G.I.
刊名: Earth and Planetary Science Letters
ISSN: 0012821X
出版年: 2020
卷: 530 语种: 英语
中文关键词: Earth's core
; Earth's magnetic field
; inertial waves
; nutation
; Ohmic dissipation
英文关键词: Geology
; Mathematical models
; Earth's core
; Earth's magnetic field
; Inertial waves
; nutation
; Ohmic dissipation
; Magnetic fields
; Ekman layer
; energy dissipation
; geomagnetic field
; inner core
; nutation
; outer core
; perturbation
英文摘要: The diurnal tidal forces can excite a normal mode of the Earth's core, the free inner core nutation (FICN), which is characterized by a tilt of the rotation axis of the inner core with respect to the rotation axis of the outer core. The differential rotation between the inner core and the outer core induces fluid motions in the outer core and gives rise to Ohmic dissipation in the presence of the Earth's internal magnetic field. Nutation measurements can reflect such dissipation if it is sufficiently strong and thus can provide insights into the properties and dynamics of the Earth's core. In this study we perform a set of numerical calculations of the linear perturbations in the outer core induced by the FICN at very low Ekman numbers (as small as 10−11). Our numerical results show that the back-reaction of the magnetic field notably alters the structure and length scale of the perturbations induced by the FICN, and thus influences the Ohmic dissipation resulting from the perturbations. When the Ekman number is sufficiently small, Ohmic dissipation tends to be insensitive to the fluid viscosity and to the magnetic diffusivity, which allows us to estimate the Ohmic dissipation associated with the FICN without relying on an extrapolation. In contrast to the results of Buffett (2010b), the estimated Ohmic dissipation based on our numerical calculations is too weak to account for the observed damping of the FICN mode. This also implies that nutation measurements cannot provide effective constraints on the strength of the magnetic field inside the Earth's outer core. © 2019 Elsevier B.V. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/165121
Appears in Collections: 气候变化与战略
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作者单位: Department of Earth and Space Sciences, Southern University of Science and Technology, Shenzhen, 518055, China; Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Centre for Mathematical Sciences, Wilberforce Road, Cambridge, CB3 0WA, United Kingdom
Recommended Citation:
Lin Y.,Ogilvie G.I.. Ohmic dissipation in the Earth's outer core resulting from the free inner core nutation[J]. Earth and Planetary Science Letters,2020-01-01,530