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| Titel |
Stability of thermal boundary layers for convection in spherical shell : Application to the dynamics of Earth mantle. |
| VerfasserIn |
L. Duchoiselle, F. Deschamps, P. J. Tackley |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250020783
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| Zusammenfassung |
| Improving the knowledge of convection into mantle of terrestrial planets required a better
understanding of its physical and chemical state. Recently, with the help of massive
computational resources, significant progresses were achieved in the numerical modeling of
planetary mantles convection. Models with a high degree of complexity (including realistic
viscosity laws, mixed mode of heating, spherical geometry, thermo-chemical convection, …)
are now available. Among the parameters that recently became accessible, spherical geometry
is a key ingredient because it affects the relative strength of the top and bottom
thermal boundary layers. Despite these progresses, many details of planetary mantles
convection remain unclear and so far, no model of Earth’s mantle convection fits all
available geophysical, geochemical, and geological constraints. Using STAGYY,
which solve the usual conservative equations of mass, energy and momentum, we
explored the on a yin-yang grid, we explored the influence of various parameters
on convection in spherical geometry. First, we have performed several numerical
experiments on varying important parameters including the Rayleigh number, the
curvature (ratio between radius of the core and the planet one), the mode of heating
(only from below or with an internal heating component), rheology (isoviscous or
temperature dependence). In particular, we studied the evolution of the style of
convection, average temperature, heat flux and critical Rayleigh number depending
on these parameters. We have then built scaling laws between the parameters and
observables, for instance between the Nusselt and Rayleigh number, and between the
temperature and curvature factor. Our results suggest that extrapolations previously made
from Cartesian models may not be valid in spherical geometry. In particular, the
dependence of temperature on curvature differs significantly from that expected by
Cartesian scaling laws. In addition, it also depends on the Rayleigh number. A possible
explanation for these discrepancies is the asymmetry between the top and bottom thermal
boundary layers, which may alter their relative stability. The new scaling laws we
obtained enable to reconsider some aspects of thermal evolution and physical states
of terrestrial planets like Earth, Mars, Mercury or some giant planets satellites. |
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