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Context: Differential rotation in stars is driven by turbulent transport of angular momentum. Aims: To measure and parametrize the non-diffusive contribution to turbulent stress, known as $\Lambda$ effect, and its quenching as a function of…

Solar and Stellar Astrophysics · Physics 2019-03-12 Petri J. Käpylä

The empirical finding with data from the Solar Dynamics Observatory (SDO) of positive (negative) horizontal Reynolds stress at the northern (southern) hemisphere for solar giant cells (Hathaway et al. 2013) is discussed for its consequences…

Solar and Stellar Astrophysics · Physics 2015-06-22 Guenther Ruediger , Manfred Kueker , Ilya Tereshin

Homogeneous anisotropic turbulence simulations are used to determine off-diagonal components of the Reynolds stress tensor and its parameterization in terms of turbulent viscosity and Lambda-effect. The turbulence is forced in an…

Astrophysics · Physics 2011-11-10 P. J. Käpylä , A. Brandenburg

(abridged) Context. Turbulent fluxes of angular momentum and heat due to rotationally affected convection play a key role in determining differential rotation of stars. Here we perform a systematic comparison between Cartesian and spherical…

Solar and Stellar Astrophysics · Physics 2011-07-07 P. J. Käpylä , M. J. Mantere , G. Guerrero , A. Brandenburg , P. Chatterjee

We study stellar convection using a local three-dimensional MHD model, with which we investigate the influence of rotation and large-scale magnetic fields on the turbulent momentum and heat transport. The former is studied by computing the…

Astrophysics · Physics 2009-11-10 P. J. Käpylä , M. J. Korpi , I. Tuominen

We studied the effect of the turbulent heat flux on the Reynolds stresses in a rotating turbulent convection. To this end we solved a coupled system of dynamical equations which includes the equations for the Reynolds stresses, the entropy…

Astrophysics · Physics 2009-11-11 N. Kleeorin , I. Rogachevskii

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 intense turbulence present in the solar convection zone is a major challenge to both theory and simulation as one tries to understand the origins of the striking differential rotation profile with radius and latitude that has been…

Astrophysics · Physics 2009-11-07 Allan Sacha Brun , Juri Toomre

In order to explain the variance of the solar rotation law during the activity minima and maxima, the angular momentum transport by rotating magnetoconvection is simulated in a convective box penetrated by an inclined azimuthal magnetic…

Solar and Stellar Astrophysics · Physics 2021-06-09 Günther Rüdiger , Manfred Küker

We propose a closure model for the transport of entropy and momentum in astrophysical turbulence, intended for application to rotating stellar convective regions. Our closure model is first presented in the Boussinesq formalism, and…

Solar and Stellar Astrophysics · Physics 2015-05-18 Pascale Garaud , Gordon I. Ogilvie , Neil Miller , Stephan Stellmach

We present results of two simulations of the convection zone, obtained by solving the full hydrodynamic equations in a section of a spherical shell. The first simulation has cylindrical rotation contours (parallel to the rotation axis) and…

Astrophysics · Physics 2009-10-31 Francis J. Robinson , Kwing L. Chan

The $\Lambda$ effect describes a rotation-induced non-diffusive contribution to the Reynolds stress. It is commonly held responsible for maintaining the observed differential rotation of the Sun and other late-type stars. Here the…

Solar and Stellar Astrophysics · Physics 2020-02-18 Petri J. Käpylä

We present a model for the transport of anisotropic turbulence in an accretion disc. The model uses the Reynolds stress tensor approach in the mean field approximation. To study the role of convection in a protoplanetary disc, we combine…

Solar and Stellar Astrophysics · Physics 2023-11-06 E. P. Kurbatov , Ya. N. Pavlyuchenkov

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

A mean-field theory of differential rotation in a density stratified turbulent convection has been developed. This theory is based on a combined effect of the turbulent heat flux and anisotropy of turbulent convection on the Reynolds…

Fluid Dynamics · Physics 2020-04-17 I. Rogachevskii , N. Kleeorin

We present a series of 3-D nonlinear simulations of solar-like convection, carried out using the Anelastic Spherical Harmonic (ASH) code, that are designed to isolate those processes that drive and shape meridional circulations within…

Solar and Stellar Astrophysics · Physics 2015-05-20 Nicholas A. Featherstone , Mark S. Miesch

The radial gradient of the rotation rate in the near-surface shear layer (NSSL) of the Sun is independent of latitude and radius. Theoretical mean-field models have been successful in explaining this property of the solar NSSL, while global…

Solar and Stellar Astrophysics · Physics 2021-12-01 A. Barekat , M. J. Käpylä , P. J. Käpylä , E. P. Gilson , H. Ji

Aims: We determine the components of the $\Lambda$-effect tensor that quantifies the contributions to the turbulent momentum transport even for uniform rotation. Methods: Three-dimensional numerical simulations are used to study turbulent…

Astrophysics · Physics 2008-08-22 P. J. Käpylä , A. Brandenburg

(abridged) Context: Solar-like differential rotation is characterized by a rapidly rotating equator and slower poles. However, theoretical models and numerical simulations can result in a slower equator and faster poles when the rotation is…

Solar and Stellar Astrophysics · Physics 2014-10-17 P. J. Käpylä , M. J. Käpylä , A. Brandenburg

We carry out a magneto-hydrodynamic (MHD) simulation of convective dynamo in the rotating solar convective envelope driven by the solar radiative diffusive heat flux. The simulation is similar to that reported in Fan & Fang (2014) but with…

Solar and Stellar Astrophysics · Physics 2016-01-12 Yuhong Fan , Fang Fang
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