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| Titel |
Effects of Ekman number and thickness on stably stratified region below core-mantle boundary in numerical dynamo simulations in a rotating spherical shell |
| VerfasserIn |
Takashi Nakagawa, Julien Aubert |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250073471
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| Zusammenfassung |
| In the previous study [Nakagawa, 2011], this has been investigated in fluid dynamical
behaviors on stably stratified region in 300 km below core-mantle boundary (CMB) with
numerical dynamo simulations in a rotating spherical shell, which seems not for the magnetic
field generation to affect the main dynamics including stratified region but to have the filter
effect for small-scale patches of magnetic field. However, in this study, the Ekman number
was higher than the ordinary numerical dynamo simulations, which would be O(10-5). Here
we try to decrease the Ekman number as an order of 10-5 and varying the thickness of
stratified region that may be consistent with seismic analyses [Tanaka, 2007; Helffrich and
Kaneshima, 2010], which would be less than 100 km, to investigate dynamical
behavior of the dynamo action in a rotating spherical shell. The stratified region
that is the same formulation as Takehiro and Lister [2001] is implemented into
Parody-JA code [Aubert, 2005]. When lower Ekman number is used, the stratified
region may work for the filter of small-scale patches of radial magnetic field if the
Rayleigh number is high enough to be less than 1 of frequency ratio between Rossby
and buoyancy waves and the dynamics across the stratified boundary is strongly
decoupled, which is slightly different from the previous study. This means that the
different dynamics in the stratified region may exist because the radial resolution in the
previous study has been very low compared to the current cases. In the presentation,
we will also show the effect of thickness of stably stratified region below CMB
and discuss an importance of stratified region below CMB in the core dynamics. |
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