Skip to Main content Skip to Navigation
Theses

INSTABILITES ET BIFURCATIONS ASSOCIEES A LA MODELISATION
DE LA GEODYNAMO

Abstract : We investigated with a quasi-geostrophic model convection in an internally heated rapidly rotating sphere. We showed that, in the small Ekman number limit, the kinetic energy of the convective solution becomes time dependent immediately above the onset of convection (relaxation oscillations). We showed that banded structures can develop immediately above the onset in the presence of Ekman pumping. The width of these bands corresponds to a balance between Ekman pumping and bulk viscosity.
Then we investigated the dynamo bifurcation. We found that decreasing (resp. increasing) the Roberts (Ekman) number for a given Ekman (Roberts) number one successively obtains supercritical bifurcations, subcritical bifurcations and isola. We showed that for a given set of parameters, metastable dynamos can exist, loosing their stability after an arbitrary long period of time.
We also observed that several convective solutions can exist for the same parameter set. Among these solutions some do sustain dynamo action while others do not.
Complete list of metadatas

https://tel.archives-ouvertes.fr/tel-00011484
Contributor : Vincent Morin <>
Submitted on : Saturday, January 28, 2006 - 12:39:13 AM
Last modification on : Thursday, December 10, 2020 - 12:36:55 PM
Long-term archiving on: : Saturday, April 3, 2010 - 9:56:29 PM

Identifiers

  • HAL Id : tel-00011484, version 1

Citation

Vincent Morin. INSTABILITES ET BIFURCATIONS ASSOCIEES A LA MODELISATION
DE LA GEODYNAMO. Géophysique [physics.geo-ph]. Université Paris-Diderot - Paris VII, 2005. Français. ⟨tel-00011484⟩

Share

Metrics

Record views

800

Files downloads

298