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Magnetic fields are an important ingredient of the interstellar medium (ISM). Besides their importance for star formation, they govern the transport of cosmic rays, relevant to the launch and regulation of galactic outflows and winds, which…

The generation of magnetic field in an electrically conducting fluid generally involves the complicated nonlinear interaction of flow turbulence, rotation and field. This dynamo process is of great importance in geophysics, planetary…

Fluid Dynamics · Physics 2021-10-04 Steven Tobias

We report the observation of dynamo action in the VKS experiment, i.e., the generation of magnetic field by a strongly turbulent swirling flow of liquid sodium. Both mean and fluctuating parts of the field are studied. The dynamo threshold…

Magnetic fields are observed not only in stars, but in galaxies, clusters, and even high redshift Lyman-alpha systems. In principle, these fields could play an important role in structure formation and also affect the anisotropies in the…

Astrophysics · Physics 2009-10-31 Roy Maartens

A marginally excited cosmic kinematic dynamo is found in the background of a non-singular anisotropic Kasner cosmological metric solution of Einstein field equation of general relativity. The magnetic field is not amplified but is frozen…

Astrophysics · Physics 2007-07-10 L. C. Garcia de Andrade

The excitation of cosmological perturbations in an anisotropic cosmological model and in the presence of a homogeneous magnetic field has been studied, using the ideal magnetohydrodynamic (MHD) equations. In this case, the system of partial…

Astrophysics · Physics 2009-06-23 K. Kleidis , A. Kuiroukidis , D. B. Papadopoulos , L. Vlahos

The magnetic field measured in the Madison Dynamo Experiment shows intermittent periods of growth when an axial magnetic field is applied. The geometry of the intermittent field is consistent with the fastest growing magnetic eigenmode…

Plasma Physics · Physics 2009-11-11 M. D. Nornberg , E. J. Spence , R. D. Kendrick , C. M. Jacobson , C. B. Forest

The magnetorotational instability (MRI) has been proposed as the method of angular momentum transport that enables accretion in astrophysical discs. However, for weakly-ionized discs, such as protoplanetary discs, it remains unclear whether…

Instrumentation and Methods for Astrophysics · Physics 2023-09-15 Amy Secunda , Peter Donnel , Hantao Ji , Jeremy Goodman

Recent theoretical studies have suggested that a magnetic field may play a crucial role in the first star formation in the universe. However, the influence of the magnetic field on the first star formation has yet to be understood well. In…

Astrophysics of Galaxies · Physics 2021-05-26 Kenji Eric Sadanari , Kazuyuki Omukai , Kazuyuki Sugimura , Tomoaki Matsumoto , Kengo Tomida

We show that the first structures that form in the universe should spontaneously generate magnetic fields. No primordial seed field is required for this "first dynamo". Although the first dynamo starts with kinetic plasma instabilities, we…

Cosmology and Nongalactic Astrophysics · Physics 2009-05-08 Andrei Gruzinov

Magnetic fields play an important role in astrophysical accretion discs, and in the interstellar and intergalactic medium. They drive jets, suppress fragmentation in star-forming clouds and can have a significant impact on the accretion…

Plasma Physics · Physics 2016-12-30 Christoph Federrath

The origin and evolution of magnetic fields in the Universe is still an open question. Their observations in galaxies suggest strong magnetic fields already at high redshift as well as at present time. However, neither primordial magnetic…

Astrophysics of Galaxies · Physics 2017-04-21 Michael Rieder , Romain Teyssier

Cosmic ray propagation is determined by the properties of interstellar turbulence. The multiphase nature of interstellar medium (ISM) and diversity of driving mechanisms give rise to spatial variation of turbulence properties. Meanwhile,…

High Energy Astrophysical Phenomena · Physics 2021-09-21 Huirong Yan

Stably stratified layers are present in stellar interiors (radiative zones) as well as planetary interiors - recent observations and theoretical studies of the Earth's magnetic field seem to indicate the presence of a thin, stably…

Solar and Stellar Astrophysics · Physics 2019-10-10 J. Philidet , C. Gissinger , F. Lignières , L. Petitdemange

The standard magnetorotational instability (SMRI) is a promising mechanism for turbulence and rapid accretion in astrophysical disks. It is a magnetohydrodynamic (MHD) instability that destabilizes otherwise hydrodynamically stable disk…

We investigate the evolution of hydromagnetic perturbations in a small section of accretion disks. It is known that molecular viscosity is negligible in accretion disks. Hence, it has been argued that a mechanism, known as Magnetorotational…

High Energy Astrophysical Phenomena · Physics 2015-08-12 Sujit Kumar Nath , Banibrata Mukhopadhyay

The onset and evolution of magnetic fields in laboratory and astrophysical plasmas is determined by several mechanisms, including instabilities, dynamo effects and ultra-high energy particle flows through gas, plasma and interstellar-media.…

Plasma Physics · Physics 2015-05-20 A. Flacco , J. Vieira , A. Lifschitz , F. Sylla , S. Kahaly , M. Veltcheva , L. O. Silva , V. Malka

The interstellar medium (ISM) in galaxies is directly affected by the mass and energy outflows originating in regions of star formation. Magnetic fields are an essential ingredient of the ISM, but their connection to the gaseous medium and…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-05 George Heald

Initial results from the Madison Dynamo Experiment provide details of the inductive response of a turbulent flow of liquid sodium to an applied magnetic field. The magnetic field structure is reconstructed from both internal and external…

Plasma Physics · Physics 2007-05-23 M. D. Nornberg , E. J. Spence , R. D. Kendrick , C. M. Jacobson , C. B. Forest

We present numerical simulations of driven magnetohydrodynamic (MHD) turbulence with weak/moderate imposed magnetic fields. The main goal is to clarify dynamics of magnetic field growth. We also investigate the effects of the imposed…

Astrophysics · Physics 2011-02-11 J. Cho , E. Vishniac , A. Beresnyak , A. Lazarian , D. Ryu