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The origin and structure of the magnetic fields in the interstellar medium of spiral galaxies is investigated with 3D, non-ideal, compressible MHD simulations, including stratification in the galactic gravity field, differential rotation…

Astrophysics of Galaxies · Physics 2013-04-01 F. A. Gent , A. Shukurov , A. Fletcher , G. R. Sarson , M. J. Mantere

At large magnetic Reynolds numbers, magnetic helicity evolution plays an important role in astrophysical large-scale dynamos. The recognition of this fact led to the development of the dynamical alpha quenching formalism, which predicts…

Solar and Stellar Astrophysics · Physics 2012-03-08 Alexander Hubbard , Axel Brandenburg

Large-scale coherent magnetic fields observed in the nearby galaxies are thought to originate by a mean-field dynamo. This is governed via the turbulent electromotive force (EMF, $\overline{\mathcal{E}} $) generated by the helical…

Astrophysics of Galaxies · Physics 2020-11-18 Abhijit B. Bendre , Detlef Elstner , Oliver Gressel

(1)The previous theoretical studies showed that in the presence of the small-scale dynamo the large-scale vorticity can produce the the divergent-type helicity flux breaking the equatorial reflection symmetry of the magnetic fluctuations in…

Solar and Stellar Astrophysics · Physics 2026-01-13 V. V. Pipin

The nonlinear theory of a "shear-current" effect in a nonrotating and nonhelical homogeneous turbulence with an imposed mean velocity shear is developed. The ''shear-current" effect is associated with the $\bar{\bf W} {\bf \times} \bar{\bf…

Astrophysics · Physics 2009-11-10 I. Rogachevskii , N. Kleeorin

Mean-field dynamo theory suggests that turbulent convection in a rotating layer of electrically-conducting fluid produces a significant alpha-effect, which is one of the key ingredients in any mean-field dynamo model. Provided that this…

Solar and Stellar Astrophysics · Physics 2014-01-06 Benjamin Favier , Paul J. Bushby

Modelling perturbations of the Milky Way (MW) halo induced by the infall of the Large Magellanic Cloud (LMC) offers new avenues to constrain the dark matter (DM) distribution in our Galaxy. A key observable is the reflex motion of the MW…

Astrophysics of Galaxies · Physics 2025-08-08 Rashid Yaaqib , Michael Petersen , Jorge Peñarrubia

Magnetic fields correlated on kiloparsec scales are seen in spiral galaxies. Their origin could be due to amplification of a small seed field by a turbulent galactic dynamo. We review the current status of the galactic dynamo, especially…

Astrophysics · Physics 2007-05-23 Kandaswamy Subramanian

For moderate and slow rotation, magnetic activity of solar-like stars is observed to strongly depend on rotation. These observations do not yet have a solid explanation in terms of dynamo theory. We aim to find such an explanation by…

Solar and Stellar Astrophysics · Physics 2020-10-07 J. Warnecke , M. J. Käpylä

We explore the decay of turbulence and magnetic fields generated by fluctuation dynamo action in the context of galaxy clusters where such a decaying phase can occur in the aftermath of a major merger event. Using idealized numerical…

Cosmology and Nongalactic Astrophysics · Physics 2019-08-28 Sharanya Sur

Magnetic fields in nearby, star-forming galaxies reveal both large-scale patterns and small-scale structures. A large-scale field reversal may exist in the Milky Way but no such reversals have been observed so far in external galaxies. The…

Astrophysics of Galaxies · Physics 2015-05-30 David Moss , Rodion Stepanov , Tigran Arshakian , Rainer Beck , Marita Krause , Dmitri Sokoloff

In a recent paper (Phys. Rev. Lett. 94 (2005), 184506; physics/0411050) it was shown that a simple mean-field dynamo model with a spherically symmetric helical turbulence parameter alpha can exhibit a number of features which are typical…

Geophysics · Physics 2007-05-23 Frank Stefani , Gunter Gerbeth , Uwe Guenther , Mingtian Xu

We propose that grand minima in solar activity are caused by simultaneous fluctuations in the meridional circulation and the Babcock-Leighton mechanism for the poloidal field generation in the flux transport dynamo model. We present the…

Solar and Stellar Astrophysics · Physics 2015-06-16 Bidya Binay Karak , Arnab Rai Choudhuri

The origin and evolution of cosmic magnetic fields as well as the influence of the magnetic fields on the evolution of galaxies are unknown. Though not without challenges, the dynamo theory can explain the large-scale coherent magnetic…

Astrophysics of Galaxies · Physics 2016-02-17 F. S. Tabatabaei , T. P. K. Martinsson , J. H. Knapen , J. E. Beckman , B. Koribalski , B. G. Elmegreen

We present a simple semi-analytical model of nonlinear, mean-field galactic dynamos and use it to study the effects of various magnetic helicity fluxes. The dynamo equations are reduced using the `no-$z$' approximation to a nonlinear system…

Astrophysics · Physics 2008-11-26 Sharanya Sur , Anvar Shukurov , Kandaswamy Subramanian

A theory of recently discovered anomalous low-field magnetoresistance is developed for the system of two-dimensional electrons scattered by hard disks of radius $a,$ randomly distributed with concentration $n.$ For small magnetic fields the…

Mesoscale and Nanoscale Physics · Physics 2009-11-10 Vadim V. Cheianov , A. P. Dmitriev , V. Yu. Kachorovskii

It has been suggested in recent literature that nonlinear and/or gravitomagnetic general relativistic effects can play a leading role in galactic dynamics, partially or totally replacing dark matter. Using the 1+3 "quasi-Maxwell" formalism,…

General Relativity and Quantum Cosmology · Physics 2024-09-20 L. Filipe O. Costa , José Natário

The current state of research of the Galactic magnetic field is reviewed critically. The average (equipartition) strength of the total field derived from radio synchrotron data is 6 +/- 2 muG locally and about 10 +/- 3 muG at 3 kpc Galactic…

Astrophysics · Physics 2021-04-28 Rainer Beck

A generic non-symmetric magnetic field does not confine magnetized charged particles for long times due to secular magnetic drifts. Stellarator magnetic fields should be omnigeneous (that is, designed such that the secular drifts vanish),…

Plasma Physics · Physics 2014-04-07 Felix I. Parra , Ivan Calvo , Jose Luis Velasco , J. Arturo Alonso

We study the effects of a static and uniform magnetic field on the evolution of energy density fluctuations present in a medium. By numerically solving the relativistic Boltzmann-Vlasov equation within the relaxation time approximation, we…

Nuclear Theory · Physics 2023-06-01 Shreyansh S. Dave , Subrata Pal
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