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We consider viscous free-boundary magnetohydrodynamics(MHD) under vacuum in $\mathbb{R}^3$, especially when vacuum magnetic field is identically zero. It is a central problem in mathematics to perform vanishing viscosity limit to get a…

Analysis of PDEs · Mathematics 2017-04-13 Donghyun Lee

It is shown that the turbulent dynamo $\alpha$-effect converts magnetic helicity from the turbulent field to the mean field when the turbulence is electromagnetic while the magnetic helicity of the mean-field is transported across space…

Astrophysics · Physics 2008-11-26 Hantao Ji

A slightly tilted permanent magnet rotating at high speed can induce a magnetic field capable of trapping another permanent magnet in a gravity independent levitated bound state, bypassing Earnshaw's theorem. During levitation, the floater…

Classical Physics · Physics 2026-04-23 Hugo Schreckenberg , Zayneb El Omari El Alaoui , Guilhem Gallot

Magnetic helicity is approximately conserved in resistive MHD models. It quantifies the entanglement of the magnetic field within the plasma. The transport and removal of helicity is crucial in both the dynamo in the solar interior and…

Solar and Stellar Astrophysics · Physics 2020-03-25 Christopher Prior , Gareth Hawkes , Mitch Berger

With the help of a model of magnetohydrodynamic (MHD) turbulence tested previously, we explore high Reynolds number regimes up to equivalent resolutions of 6000^3 grid points in the absence of forcing and with no imposed uniform magnetic…

Fluid Dynamics · Physics 2015-03-19 J. Pietarila Graham , P. D. Mininni , A. Pouquet

Besides total energy, three-dimensional incompressible Hall magnetohydrodynamics (MHD) possesses two inviscid invariants which are the magnetic helicity and the generalized helicity. New exact relations are derived for homogeneous…

Fluid Dynamics · Physics 2016-03-30 Supratik Banerjee , Sebastien Galtier

We investigate analytically the magnetic instability in a rotating and electrically conducting fluid induced by an imposed magnetic field with its associated electric current. The short-wavelength approximation is used in the linear…

Earth and Planetary Astrophysics · Physics 2013-08-22 Xing Wei

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 consider the stability of a configuration consisting of a vertical magnetic field in a planar flow on elliptical streamlines in ideal hydromagnetics. In the absence of a magnetic field the elliptical flow is universally unstable (the…

Astrophysics · Physics 2009-11-10 Norman R. Lebovitz , Ellen G. Zweibel

We study the evolution of kinetic and magnetic energy spectra in magnetohydrodynamic flows in the presence of strong cross helicity. For forced turbulence, we find weak inverse transfer of kinetic energy toward the smallest wavenumber. This…

Fluid Dynamics · Physics 2019-02-20 Axel Brandenburg , Sean Oughton

We are concerned with the uniform regularity estimates and vanishing viscosity limit of solution to two dimensional viscous compressible magnetohydrodynamics (MHD) equations with transverse background magnetic field. When the magnetic field…

Analysis of PDEs · Mathematics 2022-09-23 Xiufang Cui , Shengxin Li , Feng Xie

We report observations of wave turbulence on the surface of a ferrofluid submitted to a magnetic field parallel to the fluid surface. The magnetic wave turbulence shows several differences compared to the normal field case reported…

Fluid Dynamics · Physics 2011-04-12 Stéphane Dorbolo , Eric Falcon

We consider the three-dimensional incompressible magnetohydrodynamics (MHD) equations in a bounded domain with small volume and free moving surface boundary. We establish a priori estimate for solutions with minimal regularity assumptions…

Analysis of PDEs · Mathematics 2022-07-05 Chenyun Luo , Junyan Zhang

We present a new theoretical picture of magnetically dominated, decaying turbulence in the absence of a mean magnetic field. We demonstrate that such turbulence is governed by the reconnection of magnetic structures, and not by ideal…

Fluid Dynamics · Physics 2021-10-13 David N. Hosking , Alexander A. Schekochihin

Motivated by the empirical finding that the known hemispheric rules for the current helicity at the solar surface are not strict, the excitation of small-scale current helicity by the influence of a large-scale helical magnetic background…

Solar and Stellar Astrophysics · Physics 2016-08-03 Guenther Ruediger , Manfred Kueker

In this short review, we present the main known features of MHD Turbulence at Low Magnetic Reynolds number, for which the flow isn't intense nor electrically conductive enough to disturb an externally applied magnetic field. The emphasis is…

Fluid Dynamics · Physics 2020-06-16 Alban Pothérat

A two-dimensional mean field dynamo model is solved where magnetic helicity conservation is fully included. The model has a negative radial velocity gradient giving rise to equatorward migration of magnetic activity patterns. In addition…

Astrophysics · Physics 2007-05-23 A. Brandenburg , P. J. Käpylä

A theory of potential vorticity (PV) mixing in a disordered (tangled) magnetic field is presented. The analysis is in the context of $\beta$-plane MHD, with a special focus on the physics of momentum transport in the stably stratified,…

Solar and Stellar Astrophysics · Physics 2020-03-25 Chang-Chun Chen , Patrick H. Diamond

The problem of determining the effective conductivity tensor of a magnetoactive turbulent plasma is considered in the approximation of isolated particles. Additional gyrotropicterms are shown to appear in the conductivity tensor in the…

Plasma Physics · Physics 2009-11-10 Otto G. Chkhetiani

Using direct numerical simulations we demonstrate that magnetic helicity exhibits a bidirectional turbulent cascade at high but finite magnetic Reynolds numbers. Despite the injection of positive magnetic helicity in the flow, we observe…

Fluid Dynamics · Physics 2017-05-23 Moritz Linkmann , Vassilios Dallas