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Numerical MHD simulations play increasingly important role for understanding mechanisms of stellar magnetism. We present simulations of convection and dynamos in density-stratified rotating spherical fluid shells. We employ a new 3D…

Solar and Stellar Astrophysics · Physics 2015-09-03 Radostin D. Simitev , Alexander G. Kosovichev , Friedrich H. Busse

To elucidate the influence of shear flow on the generation of magnetic field (the dynamo effect), we study the kinematic limit where the magnetic field does not backreact on the velocity field. By non-perturbatively incorporating the effect…

Fluid Dynamics · Physics 2009-07-09 Nicolas Leprovost , Eun-Jin Kim

Magnetic induction in magnetohydrodynamic fluids at magnetic Reynolds number (Rm) less than~1 has long been known to cause magnetic drag. Here, we show that when $\mathrm{Rm} \gg 1$ and the fluid is in a hydrodynamic-dominated regime in…

Plasma Physics · Physics 2019-09-04 Jeffrey B. Parker , Navid C. Constantinou

As well known, magnetic fields in space are distributed very inhomogeneously. Some-times field distributions have forms of filaments with high magnetic field values. As many ob-servations show, such a filamentation takes place in convective…

Solar and Stellar Astrophysics · Physics 2024-03-03 Evgeny A. Kuznetsov , Evgeny A. Mikhailov

Motivated by the significant interaction of convection, rotation and magnetic field in many astrophysical objects, we investigate the interplay between large-scale flows driven by rotating convection and an imposed magnetic field. We…

Solar and Stellar Astrophysics · Physics 2016-11-23 Laura K. Currie

Helicity, a measure of the breakage of reflectional symmetry representing the topology of turbulent flows, contributes in a crucial way to their dynamics and to their fundamental statistical properties. We review several of their main…

Plasma Physics · Physics 2022-02-16 Annick Pouquet , Nobumitsu Yokoi

To explain the large-scale magnetic field of the Sun and other bodies, mean-field dynamo theory is commonly applied where one solves the averaged equations for the mean magnetic field. However, the standard approach breaks down when the…

Solar and Stellar Astrophysics · Physics 2018-06-06 A. Brandenburg , P. Chatterjee

A quasi-linear theory is presented for how randomly forced, barotropic velocity fluctuations cause an exponentially-growing, large-scale (mean) magnetic dynamo in the presence of a uniform shear flow, $\vec{U} = S x \vec{e}_y$. It is a…

Astrophysics of Galaxies · Physics 2015-05-30 James C. McWilliams

Renormalized viscosity, renormalized resistivity, and various energy fluxes are calculated for helical magnetohydrodynamics using perturbative field theory. The calculation is to first-order in perturbation. Kinetic and magnetic helicities…

Chaotic Dynamics · Physics 2008-11-26 Mahendra K. Verma

We build on the formulation developed in Sridhar & Singh (JFM, 664, 265, 2010), and present a theory of the \emph{shear dynamo problem} for small magnetic and fluid Reynolds numbers, but for arbitrary values of the shear parameter.…

Astrophysics of Galaxies · Physics 2015-05-18 Nishant K. Singh , S. Sridhar

It is shown that flows in precessing cubes develop at certain parameters large axisymmetric components in the velocity field which are large enough to either generate magnetic fields by themselves, or to contribute to the dynamo effect if…

Fluid Dynamics · Physics 2019-05-22 O. Goepfert , A. Tilgner

Understanding large-scale magnetic field growth in astrophysical objects is a persistent challenge. We tackle the long-standing question of how much helical large-scale dynamo growth occurs independent of the magnetic Reynolds number (Rm)…

Plasma Physics · Physics 2023-03-13 Hongzhe Zhou , Eric Blackman

A conducting Taylor-Couette flow with quasi-Keplerian rotation law containing a toroidal magnetic field serves as a mean-field dynamo model of the Tayler-Spruit-type. The flows are unstable against nonaxisymmetric perturbations which form…

Solar and Stellar Astrophysics · Physics 2020-02-12 G. Rüdiger , M. Schultz

The meniscal tissue is a layered material with varying properties influenced by collagen content and arrangement. Understanding the relationship between structure and properties is crucial for disease management, treatment development, and…

Computational Engineering, Finance, and Science · Computer Science 2023-07-26 J. Waghorne , F. P. Bonomo , A. Rabbani , D. Bell , O. Barrera

The flow transformation and the generation of vortex structures by a strong magnetic dipole field in a liquid metal duct flow is studied by means of three-dimensional direct numerical simulations. The dipole is considered as the paradigm…

Fluid Dynamics · Physics 2013-11-13 Saskia Tympel , Thomas Boeck , Jörg Schumacher

The effect of a spatially uniform magnetic field on the shear rheology of a dilute emulsion of monodispersed ferrofluid droplets, immersed in a non-magnetizable immiscible fluid, is investigated using direct numerical simulations. The…

Soft Condensed Matter · Physics 2021-08-04 Paolo Capobianchi , Marcello Lappa , Mónica S. N. Oliveira , Fernando T. Pinho

We performed kinematic studies of the evolution of small-scale magnetic fields in the surface laters of M-dwarfs. We solved the induction equation for a prescribed velocity field, magnetic Reynolds number, and boundary conditions in a…

Astrophysics · Physics 2009-11-07 S. B. F. Dorch , H. -G. Ludwig

We study the magneto-rotational instability (MRI) driven dynamo in a geometrically thin disc ($H/R\ll 1$) using stratified zero net flux (ZNF) shearing box simulations. We find that mean fields and EMFs oscillate with a primary frequency…

High Energy Astrophysical Phenomena · Physics 2024-07-22 Prasun Dhang , Abhijit Bendre , Kandaswamy Subramanian

A crucial point for the understanding of the von-K\'arm\'an-Sodium (VKS) dynamo experiment is the influence of soft-iron impellers. We present numerical simulations of a VKS-like dynamo with a localized permeability distribution that…

Computational Physics · Physics 2012-08-08 Andre Giesecke , Frank Stefani , Gunter Gerbeth

The effects of a vertical static magnetic field on the flow structure and global transport properties of momentum and heat in liquid metal Rayleigh-B\'enard convection are investigated. Experiments are conducted in a cylindrical convection…

Fluid Dynamics · Physics 2020-05-13 Till Zürner , Felix Schindler , Tobias Vogt , Sven Eckert , Jörg Schumacher