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| Titel |
Non-equilibrium effects of core-cooling and time-dependent internal heating on mantle flush events |
| VerfasserIn |
D. A. Yuen, S. Balachandar, V. C. Steinbach, S. Honda, D. M. Reuteler, J. J. Smedsmo, G. S. Lauer |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1023-5809
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| Digitales Dokument |
URL |
| Erschienen |
In: Nonlinear Processes in Geophysics ; 2, no. 3/4 ; Nr. 2, no. 3/4, S.206-221 |
| Datensatznummer |
250000255
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| Publikation (Nr.) |
 copernicus.org/npg-2-206-1995.pdf |
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| Zusammenfassung |
| We have examined the non-equilibrium effects of core-cooling
and time-dependent internal-heating on the thermal evolution of the Earth's mantle and on
mantle flush events caused by the two major phase transitions. Both two- and
three-dimensional models have been employed. The mantle viscosity responds to the secular
cooling through changes in the averaged temperature field. A viscosity which decreases
algebraically with the average temperature has been considered. The time-dependent
internal-heating is prescribed to decrease exponentially with a single decay time. We have
studied the thermal histories with initial Rayleigh numbers between 2 x 107 and
108 .
Flush events, driven by the non-equilibrium forcings, are much more dramatic than those
produced by the equilibrium boundary conditions and constant internal heating. Multiple
flush events are found under non-equilibrium conditions in which there is very little
internal heating or very fast decay rates of internal-heating. Otherwise, the flush events
take place in a relatively continuous fashion. Prior to massive flush events small-scale
percolative structures appear in the 3D temperature fields. Time-dependent signatures,
such as the surface heat flux, also exhibits high frequency oscillatory patterns prior to
massive flush events. These two observations suggest that the flush event may be a
self-organized critical phenomenon. The Nusselt number as a function of the time-varying
Ra does not follow the Nusselt vs. Rayleigh number power-law relationship based on
equilibrium (constant temperature) boundary conditions. Instead Nu(t) may vary
non-monotonically with time because of the mantle flush events. Convective processes in
the mantle operate quite differently under non-equilibrium conditions from its
behaviour under the usual equilibrium situations. |
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