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| Titel |
Thermal convection in a planetary mantle crystallizing from a magma ocean |
| VerfasserIn |
Renaud Deguen, Stephane Labrosse, Adrien Morison |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250110019
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| Publikation (Nr.) |
 EGU/EGU2015-9981.pdf |
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| Zusammenfassung |
| In a number of geophysical or planetological settings, including a silicate mantle crystallizing
from a magma ocean, an ice shell surrounding a deep water ocean, or Earth’s inner core,
a convecting crystalline layer is in contact with a layer of its melt. Allowing for
melting/freezing at one or both of the boundaries of the solid layer is likely to affect the
pattern of convection in the layer. We study here the onset of thermal convection in a viscous
spherical shell with dynamically induced melting/freezing at either or both of its boundaries.
It is shown that the behavior of each interface depends on the value of a dimensionless
number P (one for each boundary), which is the ratio of a melting/freezing timescale
over a viscous relaxation timescale. A small value of P corresponds to permeable
boundary conditions, while a large value of P corresponds to impermeable boundary
conditions. The linear stability analysis predicts a significant effect of semi-permeable
boundaries when the number P characterizing either of the boundary is small enough:
allowing for melting/freezing at either of the boundaries results in the emergence
of larger scale convective modes. In the case of a spherical shell with permeable
inner and outer boundaries (i.e. a mantle starting to crystallize from an intermediate
depth), the most unstable mode consists in a global translation of the solid shell,
with no deformation. Numerical simulations above the convection onset show that
allowing for melting/freezing at one boundary still promotes larger scale convective
motions, and has also a strong influence on the heat flux and thermal structure. |
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