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Toroidal magnetic fields subject to the Tayler instability can transport angular momentum. We show that the Maxwell and Reynolds stress of the nonaxisymmetric field pattern depend linearly on the shear in the cylindrical gap geometry.…

Astrophysics · Physics 2009-11-13 M. Gellert , G. Rüdiger

Angular momentum transport owing to hydrodynamic turbulent convection is studied using local three dimensional numerical simulations employing the shearing box approximation. We determine the turbulent viscosity from non-rotating runs over…

Solar and Stellar Astrophysics · Physics 2011-07-07 Petri J. Käpylä , Axel Brandenburg , Maarit J. Korpi , Jan E. Snellman , Ramesh Narayan

The potential of the nonaxisymmetric magnetic instability to transport angular momentum and to mix chemicals is probed considering the stability of a nearly uniform toroidal field between conducting cylinders with different rotation rates.…

Solar and Stellar Astrophysics · Physics 2015-05-13 G. Ruediger , M. Gellert , M. Schultz

The stability problem of MHD Taylor-Couette flows with toroidal magnetic fields is considered in dependence on the magnetic Prandtl number. Only the most uniform (but not current-free) field with B\_in = B\_out has been considered. For high…

Astrophysics · Physics 2008-09-22 M. Gellert , G. Ruediger

Aims: To investigate the stability and angular momentum transport by the strato-rotational instability in the nonlinear regime. Methods: The hydrodynamic compressible equations are solved in a cartesian box in which the outer cylinder is…

Astrophysics · Physics 2007-05-23 A. Brandenburg , G. Ruediger

We demonstrate with a nonlinear MHD code that angular momentum can be transported due to the magnetic instability of toroidal fields under the influence of differential rotation, and that the resulting effective viscosity may be high enough…

Solar and Stellar Astrophysics · Physics 2015-06-19 G. Ruediger , M. Gellert , F. Spada , I. Tereshin

The turbulent diffusion tensor describing the evolution of the mean concentration of a passive scalar is investigated for non-helically forced turbulence in the presence of rotation or a magnetic field. With rotation, the Coriolis force…

Solar and Stellar Astrophysics · Physics 2009-05-09 Axel Brandenburg , Andreas Svedin , Geoffrey M. Vasil

Azimuthal magnetorotational instability is a mechanism that generates nonaxisymmetric field pattern. Nonlinear simulations in an infinite Taylor-Couette system with current-free external field show, that not only the linearly unstable mode…

Astrophysics · Physics 2009-11-13 M. Gellert , G. Ruediger , A. Fournier

Context: Rotating anisotropic convection generates differential rotation in stellar convection zones. Aims: The main aim is to compute the non-diffusive contribution ($\Lambda$ effect) to angular momentum transport, described by Reynolds…

Solar and Stellar Astrophysics · Physics 2026-03-11 P. J. Käpylä

Small levels of turbulence can be present in stellar radiative interiors due to, e.g., instability of rotational shear. In this paper we estimate turbulent transport coefficients for stably stratified rotating stellar radiation zones.…

Solar and Stellar Astrophysics · Physics 2012-05-23 L. L. Kitchatinov , A. Brandenburg

According to Rayleigh's criterion, rotating flows are linearly stable when their specific angular momentum increases radially outward. The celebrated magnetorotational instability opens a way to destabilize those flows, as long as the…

Fluid Dynamics · Physics 2015-11-23 Frank Stefani , Oleg N. Kirillov

The instability of a quasi-Kepler flow in dissipative Taylor-Couette systems under the presence of an homogeneous axial magnetic field is considered with focus to the excitation of nonaxisymmetric modes and the resulting angular momentum…

Solar and Stellar Astrophysics · Physics 2015-05-30 M. Gellert , G. Rüdiger , M. Schultz

In this paper we argue that differential rotation can possibly sustain hydrodynamic turbulence in the absence of magnetic field. We explain why the non-linearities of the hydrodynamic equations (i.e. turbulent diffusion) should not be…

Astrophysics · Physics 2009-11-10 D. T. Richard

It is known that in a hydrodynamic Taylor-Couette system uniform rotation or a rotation law with positive shear ('super-rotation') are linearly stable. It is also known that a conducting fluid under the presence of a sufficiently strong…

Solar and Stellar Astrophysics · Physics 2016-02-17 G. Rüdiger , M. Schultz , M. Gellert , F. Stefani

We experimentally and numerically investigate the angular momentum transport in turbulent Taylor-Couette flow for independently rotating cylinders at a small radius ratio of $\eta=0.357$ for various shear Reynolds numbers ($4.5\times 10^3…

We provide a consistent theory of turbulence in the presence of shear and rotation. Starting from a quasi-linear equation for the fluctuating fields, we derive turbulence amplitude and turbulent transport coefficients, taking into account…

Fluid Dynamics · Physics 2009-11-13 Nicolas Leprovost , Eun-Jin Kim

The principles underlying a proposed class of black hole accretion models are examined. The flows are generally referred to as ``convection-dominated,'' and are characterized by inward transport of angular momentum by thermal convection and…

Astrophysics · Physics 2009-11-07 Steven A. Balbus , John F. Hawley

The Tayler instability of an azimuthal magnetic field with one or two ``rings'' along the radius is studied for an axially unbounded Taylor-Couette flow. The rotation law of the conducting fluid is a quasi-Keplerian one. Without rotation…

Solar and Stellar Astrophysics · Physics 2025-03-18 Günther Rüdiger , Manfred Schultz

Decades ago S. Lundquist, S. Chandrasekhar, P.H. Roberts and R. J.~Tayler first posed questions about the stability of Taylor-Couette flows of conducting material under the influence of large-scale magnetic fields. These and many new…

Plasma Physics · Physics 2018-05-23 Günther Rüdiger , Marcus Gellert , Rainer Hollerbach , Manfred Schultz , Frank Stefani

The linear stability of MHD Taylor-Couette flow of infinite vertical extension is considered for various magnetic Prandtl numbers Pm. The calculations are performed for a wide gap container with \hat\eta=0.5 with an axial uniform magnetic…

Astrophysics · Physics 2016-08-16 D. A. Shalybkov , G. Rüdiger , M. Schultz
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