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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…

偏微分方程分析 · 数学 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…

天体物理学 · 物理学 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…

经典物理 · 物理学 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…

太阳与恒星天体物理 · 物理学 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…

流体动力学 · 物理学 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…

流体动力学 · 物理学 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…

地球与行星天体物理 · 物理学 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…

天体物理学 · 物理学 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…

天体物理学 · 物理学 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…

流体动力学 · 物理学 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…

偏微分方程分析 · 数学 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…

流体动力学 · 物理学 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…

偏微分方程分析 · 数学 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…

流体动力学 · 物理学 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…

太阳与恒星天体物理 · 物理学 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…

流体动力学 · 物理学 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…

天体物理学 · 物理学 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,…

太阳与恒星天体物理 · 物理学 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…

等离子体物理 · 物理学 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…

流体动力学 · 物理学 2017-05-23 Moritz Linkmann , Vassilios Dallas