Open AccessEarth core motions: experiments with spheroids
Author(s) -
Vanyo J. P.
Publication year - 1984
Publication title -
geophysical journal of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.302
H-Index - 168
eISSN - 1365-246X
pISSN - 0016-8009
DOI - 10.1111/j.1365-246x.1984.tb01930.x
Subject(s) - precession , mantle (geology) , inner core , earth's rotation , dissipation , geophysics , geology , outer core , scaling , core–mantle boundary , turbulence , core (optical fiber) , physics , spheroid , geodesy , mechanics , geometry , chemistry , optics , thermodynamics , mathematics , biochemistry , astronomy , in vitro
Summary. A series of Earth core motion experiments was completed using liquid‐filled spheroidal cavities with ellipticities (a‐b)/a =+ 1/55, + 1/400, and ‐1/400. The +1/400 cavity was tested in both smooth and rough walled versions to assess possible effects of a non‐smooth mantle‐core boundary. The experiments and analysis continue an earlier paper (Vanyo & Paltridge), that applied spherical cavity models to Earth core motions driven by precession. The +1/400 spheroid with precession rates spin rates achieves Ekman numbers ±10 ‐7 and indicates energy dissipation rates proportional to precession rates squared, consistent with models that assume liquid motions driven by precession. Results to date suggest stability/turbulence scaling factors may preclude laboratory verification of Earth core values. An earth core model extrapolated to ±10 ‐10 with an ‘effectively rigidized’ liquid core separated from the mantle by a coupling layer ± 50m thick produces a westward drift ∼ 0.2°yr ‐1 and an energy production rate ∼ 10 21 erg s −1 .