Séminaire ISTerre

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Parameter study in 3D geodynamo simulations: field generation mechanisms and transition between different regimes

jeudi 23 janvier 2020 - 10h45

Melissa Menu - LPP/LERMA
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The objective of this study is to understand the impact of parameters on the generation of magnetic fields by dynamo effect, using two models: a local model (TURBO code) and a global model (PaRoDy code). Particular attention is paid to the temporal dynamics of the system, as well as to the topology of the generated field. The local study revealed that an inverse cascade of hybrid helicity allows the transport of magnetic energy to larger scales under certain conditions (type of the wave injected, tilt angle between the magnetic field and the axis of rotation etc). The global study also shows the key role of the magnetic Prandtl number in the type of large-scale magnetic field maintained, especially in moderately turbulent regimes. A study of the force balance in these simulations highlighted the dynamics occuring at large scale between the Lorentz force and inertia. These results could be applied to a variety of systems, including the geomagnetic field during reversals.

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Equipe organisatrice : Géodynamo

Salle Dolomieu, Maison des Géosciences, 38400 Saint Martin d'Hères