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In many astrophysical environments, self-gravity can generate kinetic energy, which, in principle, is available for driving dynamo action. Using direct numerical simulations, we show that in unstirred self-gravitating subsonic turbulence…

Astrophysics of Galaxies · Physics 2022-04-20 Axel Brandenburg , Evangelia Ntormousi

This is a brief review of the main results of our recent studies of the nonlinear evolution of the small-scale MHD dynamo in the high-Prandtl-number regime and of the structure of the resulting saturated state of the isotropic homogeneous…

Astrophysics · Physics 2007-05-23 A. A. Schekochihin , S. C. Cowley , G. W. Hammett , J. L. Maron , J. C. McWilliams

Turbulent motions are essential to the mixing of entrained fluids and are also capable of amplifying weak initial magnetic fields by small-scale dynamo action. Here we perform a systematic study of turbulent mixing in magnetized media,…

Astrophysics of Galaxies · Physics 2015-06-18 Sharanya Sur , Liubin Pan , Evan Scannapieco

Additional physics beyond standard hydrodynamics is needed to fully model the intracluster medium (ICM); however, as we move to more sophisticated models, it is important to consider the role of magnetic fields and the way the fluid…

Cosmology and Nongalactic Astrophysics · Physics 2016-08-04 Hilary Egan , Brian W. O'Shea , Eric Hallman , Jack Burns , Hao Xu , David Collins , Hui Li , Michael L. Norman

The dynamo instability is investigated in the limit of infinite magnetic Prandtl number. In this limit the fluid is assumed to be very viscous so that the inertial terms can be neglected and the flow is slaved to the forcing. The forcing…

Fluid Dynamics · Physics 2015-05-20 Alexandros Alexakis

It is shown, using results of direct numerical simulations, that the spontaneous breaking of local reflectional symmetry (and corresponding localized kinetic and magnetic helicities) can dominate chaotic dynamics of the small-scale MHD…

Fluid Dynamics · Physics 2022-09-14 A. Bershadskii

Assisted with Magnetospheric Multiscale (MMS) mission capturing unprecedented high-resolution data in the terrestrial magnetotail, we apply a local streamline-topology classification methodology to investigate the categorization of the…

Plasma Physics · Physics 2023-11-28 S. Y. Huang , J. Zhang , Q. Y. Xiong , Z. G. Yuan , K. Jiang , S. B. Xu , Y. Y. Wei , R. T. Lin , L. Yu , Z. Wang

Numerical simulations of the magnetorotational instability (MRI) with zero initial net flux in a non-stratified isothermal cubic domain are used to demonstrate the importance of magnetic boundary conditions.In fully periodic systems the…

High Energy Astrophysical Phenomena · Physics 2011-07-08 Petri J. Käpylä , Maarit J. Korpi

Turbulence is a complex physical process prevalent in modern physics, particularly in ionized environments like interstellar gas, where magnetic fields play a dynamic role. However, the precise influence of magnetic fields in such settings…

Astrophysics of Galaxies · Physics 2025-08-12 Guang-Xing Li , Mengke Zhao

We relate the intermittent fluctuations of velocity gradients in turbulence to a whole range of local dissipation scales generalizing the picture of a single mean dissipation length. The statistical distribution of these local dissipation…

Fluid Dynamics · Physics 2007-10-29 Joerg Schumacher

We analyze the initial, kinematic stage of magnetic field evolution in an isotropic and homogeneous turbulent conducting fluid with a rough velocity field, v(l) ~ l^alpha, alpha<1. We propose that in the limit of small magnetic Prandtl…

Astrophysics · Physics 2007-05-23 Stanislav Boldyrev , Fausto Cattaneo

We investigate how the strength of the Lorentz force alters stellar convection zone dynamics in a suite of buoyancy-dominated, three-dimensional, spherical shell convective dynamo models. This is done by varying only the magnetic Prandtl…

Solar and Stellar Astrophysics · Physics 2025-08-28 Krista M. Soderlund , Paula Wulff , Petri Käpylä , Jonathan M. Aurnou

Variational turbulence is among the few approaches providing rigorous results in turbulence. In addition, it addresses a question of direct practical interest, namely the rate of energy dissipation. Unfortunately, only an upper bound is…

Fluid Dynamics · Physics 2009-10-28 Thierry Alboussiere

We derive relations for the decay of the kinetic and magnetic energies and the growth of the Taylor and integral scales in unforced, incompressible, homogeneous and isotropic three-dimensional magnetohydrodynamic (3DMHD) turbulence with…

Statistical Mechanics · Physics 2009-11-10 Chirag Kalelkar , Rahul Pandit

Understanding the numerical dependencies that act on the galactic dynamo is a crucial step in determining what resolution and what conditions are required to properly capture the magnetic fields observed in galaxies. Here, we present an…

Astrophysics of Galaxies · Physics 2023-05-03 Robert Wissing , Sijing Shen

The small-scale kinematic dynamo in a two-dimensional chaotic flow is studied. The analytic approach is developed in framework of the Kraichnan-Kazantsev model. It is shown that the growth of magnetic field $\bm{B}$ fluctuations stops at…

Chaotic Dynamics · Physics 2016-03-30 Igor Kolokolov

We compute numerically the threshold for dynamo action in Taylor-Green swirling flows. Kinematic calculations, for which the flow field is fixed to its time averaged profile, are compared to dynamical runs for which both the Navier-Stokes…

Many astrophysical bodies harbor magnetic fields that are thought to be sustained by a dynamo process. However, it has been argued that the production of large-scale magnetic fields by mean-field dynamo action is strongly suppressed at…

Astrophysics of Galaxies · Physics 2013-01-22 Fabio Del Sordo , Gustavo Guerrero , Axel Brandenburg

Spectropolarimetric observations show that many low-mass stars possess large-scale poloidal magnetic fields with considerable dipole component, which in some cases exhibit temporal dynamics - cycles or reversals. Although it is widely…

Solar and Stellar Astrophysics · Physics 2025-07-02 Anna Guseva , Ludovic Petitdemange , Charly Pinçon

Evolution of stochastically homogeneous magnetic field advected by incompressible turbulent flow with large magnetic Prandtl numbers is considered at the scales less than Kolmogorov viscous scale. It is shown that, despite unlimited growth…

Fluid Dynamics · Physics 2023-10-26 K. P. Zybin , A. S. Il'yn , A. V. Kopyev , V. A. Sirota