2008/05/09 by F. Rincon, G. I. Ogilvie, G.I. Ogilvie +3
Biochemistry, Genetics and Molecular Biology · Physics and Astronomy · #Angular momentum #Astrophysics and Star Formation Studies #Dynamo #Dynamo theory #Geomagnetism and Paleomagnetism Studies #Magnetohydrodynamics #Rotational symmetry #Shear (geology) #Shear flow #Solar and Space Plasma Dynamics #Toroid #Turbulence #astro-ph
paper · pdf · doi:10.1002/asna.200811010
12 pages. Submitted to Astronomische Nachrichten (2007 Catania MHD Workshop special issue)
arxiv created 2008/05/09 · openalex publication_date 2008/09/01 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
Abstract Identifying generic physical mechanisms responsible for the generation of magnetic fields and turbulence in differentially rotating flows is fundamental to understand the dynamics of astrophysical objects such as accretion disks and stars. In this paper, we discuss the concept of subcritical dynamo action and its hydrodynamic analogue exemplified by the process of nonlinear transition to turbulence in non‐rotating wall‐bounded shear flows. To illustrate this idea, we describe some recent results on nonlinear hydrodynamic transition to turbulence and nonlinear dynamo action in rotating shear flows pertaining to the problem of turbulent angular momentum transport in accretion disks. We argue that this concept is very generic and should be applicable to many astrophysical problems involving a shear flow and non‐axisymmetric instabilities of shearinduced axisymmetric toroidal velocity or magnetic fields, such as Kelvin‐Helmholtz, magnetorotational, Tayler or global magnetoshear instabilities. In the light of several recent numerical results, we finally suggest that, similarly to a standard linear instability, subcritical MHD dynamo processes in high‐Reynolds number shear flows could act as a large‐scale driving mechanism of turbulent flows that would in turn generate an independent small‐scale dynamo. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)