Dissipative effects on the sustainment of a magnetorotational dynamo in Keplerian shear flow

Autor: F. Rincon, Geoffroy Lesur, Pierre-Yves Longaretti, Gordon I. Ogilvie, Carlo Cossu, A. Riols
Přispěvatelé: Institut de recherche en astrophysique et planétologie (IRAP), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Institut de mécanique des fluides de Toulouse (IMFT), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT), Institut de Planétologie et d'Astrophysique de Grenoble (IPAG ), Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS), Department of Applied Mathematics and Theoretical Physics (DAMTP), University of Cambridge [UK] (CAM), Centre National de la Recherche Scientifique - CNRS (FRANCE), Institut National Polytechnique de Toulouse - Toulouse INP (FRANCE), Université Grenoble Alpes - UGA (FRANCE), University of Cambridge (UNITED KINGDOM), Université Toulouse III - Paul Sabatier - UT3 (FRANCE)
Jazyk: angličtina
Rok vydání: 2014
Předmět:
Angular momentum
Accretion
Mécanique des fluides
FOS: Physical sciences
Magnetic Reynolds number
Astrophysics
[SPI.MECA.MEFL]Engineering Sciences [physics]/Mechanics [physics.med-ph]/Fluids mechanics [physics.class-ph]
Physics::Fluid Dynamics
symbols.namesake
Magnetic Prandtl number
Solar and Stellar Astrophysics (astro-ph.SR)
High Energy Astrophysical Phenomena (astro-ph.HE)
Earth and Planetary Astrophysics (astro-ph.EP)
Physics
Turbulence
Reynolds number
Accretion disks – Dynamo – Instabilities – Magnetohydrodynamics (MHD) – Turbulence
Astronomy and Astrophysics
Mechanics
Astrophysics - Solar and Stellar Astrophysics
Space and Planetary Science
Dissipative system
symbols
Shear flow
Astrophysics - High Energy Astrophysical Phenomena
Dynamo
Astrophysics - Earth and Planetary Astrophysics
Zdroj: Astronomy and Astrophysics-A&A
Astronomy and Astrophysics-A&A, 2015, 575, pp.A14. ⟨10.1051/0004-6361/201424324⟩
ISSN: 0004-6361
DOI: 10.1051/0004-6361/201424324⟩
Popis: The magnetorotational (MRI) dynamo has long been considered one of the possible drivers of turbulent angular momentum transport in astrophysical accretion disks. However, various numerical results suggest that this dynamo may be difficult to excite in the astrophysically relevant regime of magnetic Prandtl number (Pm) significantly smaller than unity, for reasons currently not well understood. The aim of this article is to present the first results of an ongoing numerical investigation of the role of both linear and nonlinear dissipative effects in this problem. Combining a parametric exploration and an energy analysis of incompressible nonlinear MRI dynamo cycles representative of the transitional dynamics in large aspect ratio shearing boxes, we find that turbulent magnetic diffusion makes the excitation and sustainment of this dynamo at moderate magnetic Reynolds number (Rm) increasingly difficult for decreasing Pm. This results in an increase in the critical Rm of the dynamo for increasing kinematic Reynolds number (Re), in agreement with earlier numerical results. Given its very generic nature, we argue that turbulent magnetic diffusion could be an important determinant of MRI dynamo excitation in disks, and may also limit the efficiency of angular momentum transport by MRI turbulence in low Pm regimes.
7 pages, 6 figures
Databáze: OpenAIRE
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