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We study the evolution of a stochastic helical magnetic field generated in the early Universe after the electroweak phase transition, using standard magnetohydrodynamics (MHD). We find how the coherence length xi, magnetic energy E_M and…

Astrophysics · Physics 2017-08-23 Mark Hindmarsh , M. Christensson , A. Brandenburg

We study the evolution of primordial magnetic fields until the recombination epoch, which is constrained by the conservation of magnetic helicity density if they are maximally helical and by the Hosking integral if they are non-helical. We…

Cosmology and Nongalactic Astrophysics · Physics 2025-08-07 Fumio Uchida , Motoko Fujiwara , Kohei Kamada , Jun'ichi Yokoyama

We study compressible MHD turbulence, which holds key to many astrophysical processes, including star formation and cosmic ray propagation. To account for the variations of the magnetic field in the strongly turbulent fluid we use wavelet…

Astrophysics of Galaxies · Physics 2015-05-18 Grzegorz Kowal , Alex Lazarian

Recent MHD dynamo simulations for magnetic Prandtl number $>1$ demonstrate that when MHD turbulence is forced with sufficient kinetic helicity, the saturated magnetic energy spectrum evolves from having a single peak below the forcing scale…

Astrophysics · Physics 2009-11-07 Eric G. Blackman

We study the evolution of QCD phase transition-generated magnetic fields in freely decaying MHD turbulence of the expanding Universe. We consider a magnetic field generation model that starts from basic non-perturbative QCD theory and…

Cosmology and Nongalactic Astrophysics · Physics 2012-10-18 Alexander G. Tevzadze , Leonard Kisslinger , Axel Brandenburg , Tina Kahniashvili

Results are presented of direct numerical simulations of incompressible, homogeneous magnetohydrodynamic turbulence without a mean magnetic field, subject to different mechanical forcing functions commonly used in the literature.…

Fluid Dynamics · Physics 2018-01-29 Mairi E. McKay , Moritz Linkmann , Daniel Clark , Adam A. Chalupa , Arjun Berera

We explore the phenomenon of the recently discovered inverse transfer of energy from small to large scales in decaying magnetohydrodynamical turbulence by Brandenburg et al. (2015) even for nonhelical magnetic fields. For this investigation…

Cosmology and Nongalactic Astrophysics · Physics 2017-11-15 Johannes Reppin , Robi Banerjee

We construct a magnetic helicity conserving dynamo theory which incorporates a calculated magnetic helicity current. In this model the fluid helicity plays a small role in large scale magnetic field generation. Instead, the dynamo process…

Astrophysics · Physics 2009-10-31 Ethan T. Vishniac , Jungyeon Cho

We report results of a three dimensional, high resolution (up to 512^3) numerical investigation of supersonic compressible magnetohydrodynamic turbulence. We consider both forced and decaying turbulence. The model parameters are appropriate…

Astrophysics · Physics 2009-10-30 James M. Stone , Eve C. Ostriker , Charles F. Gammie

The energy of the stochastic magnetic field is bounded from below by a topological quantity expressing the degree of linkage of the field lines. When the bound is saturated one can assume that the storage of a certain magnetic energy…

Plasma Physics · Physics 2007-05-23 F. Spineanu , M. Vlad

Supersonic turbulence in the interstellar medium (ISM) is believed to decay rapidly within a flow crossing time irrespective of the degree of magnetization. However, this general consensus of decaying magnetohydrodynamic (MHD) turbulence…

Astrophysics of Galaxies · Physics 2013-12-10 Chang-Goo Kim , Shantanu Basu

Magnetic helicity is conserved under ideal magnetohydrodynamics (MHD) and quasi-conserved even under a resistive process. The standard definition for magnetic helicity cannot be applied directly to an open magnetic field in a volume,…

Solar and Stellar Astrophysics · Physics 2020-05-27 Kai E. Yang , Michael S. Wheatland , Stuart A. Gilchrist

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

The effect of shear on the growth of large scale magnetic fields in helical turbulence is investigated. The resulting large-scale magnetic field is also helical and continues to evolve, after saturation of the small scale field, on a slow…

Astrophysics · Physics 2007-05-23 A. Bigazzi , A. Brandenburg , K. Subramanian

We present Direct Numerical Simulations of decaying Magnetohydrodynamic (MHD) turbulence at low magnetic Reynolds number. The domain considered is bounded by periodic boundary conditions in the two directions perpendicular to the magnetic…

Fluid Dynamics · Physics 2015-03-19 Kacper Kornet , Alban Potherat

Forced turbulence simulations are used to determine the turbulent kinematic viscosity, nu_t, from the decay rate of a large scale velocity field. Likewise, the turbulent magnetic diffusivity, eta_t, is determined from the decay of a large…

Astrophysics · Physics 2007-05-23 T. A. Yousef , A. Brandenburg , G. Rüdiger

Decaying three-dimensional (3D) turbulence is studied via direct numerical simulations (DNS) for an isotropic non-rotating flow and for rotating flows with and without helicity. We analyze the cases of moderate Rossby number and large…

Fluid Dynamics · Physics 2015-05-14 T. Teitelbaum , P. D. Mininni

Helical magnetohydrodynamic turbulence with Hall effects is ubiquitous in heliophysics and plasma physics, such as star formation and solar activities, and its intrinsic mechanisms are still not clearly explained. Direct numerical…

Plasma Physics · Physics 2024-05-07 Running Hu , Jin-Han Xie , Xinliang Li , Changping Yu , Yuan Hu , Jianchun Wang , Shiyi Chen

The shell-to-shell energy transfer rates for magnetohydrodynamic (MHD) turbulence are computed analytically, which shows local energy transfer rates from velocity to velocity, velocity to magnetic, magnetic to velocity, and magnetic to…

Chaotic Dynamics · Physics 2020-06-16 Mahendra K. Verma , Arvind Ayyer , Amar V. Chandra

The effect of non periodic boundary conditions on decaying two-dimensional magnetohydrodynamic turbulence is investigated. We consider a circular domain with no-slip boundary conditions for the velocity and where the normal component of the…

Classical Physics · Physics 2009-11-13 Salah Neffaa , Wouter Bos , Kai Schneider