Article
Mechanics
S. Molokov, A. Pedcenko, R. Chahine, N. Chailly
Summary: In aluminum reduction cells, uneven electric current density at the cathode may lead to undesirable MHD instabilities, possibly due to rotating flow of liquid metal around mud spots and deep depressions caused by centrifugal forces.
Article
Physics, Multidisciplinary
Antonios Tsokaros, Milton Ruiz, Stuart L. Shapiro, Koji Uryu
Summary: This study performs the first magnetohydrodynamic simulations in full general relativity of self-consistent rotating neutron stars with ultrastrong mixed poloidal and toroidal magnetic fields. The simulations show that the neutron stars eventually succumb to various instabilities. Differential rotation spontaneously develops in the cores of the magnetars, but is eventually converted back to uniform rotation. The simulations also reveal the presence of significant ejecta, but not the necessary highly collimated, helical magnetic fields or incipient jets for gamma-ray bursts.
PHYSICAL REVIEW LETTERS
(2022)
Article
Astronomy & Astrophysics
Loren E. Held, Henrik N. Latter
Summary: Research shows that convection and the magnetorotational instability interact significantly in angular momentum transport, resulting in different flow characteristics in different phases. Convection forms large-scale and oscillatory convective cells in the nonlinear phase, helping the MRI persist to lower Rm values.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Suoqing Ji, Jim Fuller, Daniel Lecoanet
Summary: The Tayler instability is a poorly studied magnetohydrodynamic instability that is likely to occur in stellar interiors. The non-linear saturation of the instability is not well understood, but it has crucial consequences for dynamo action and angular momentum transport in radiative regions of stars.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Lizhong Zhang, Omer Blaes, Yan-Fei Jiang
Summary: The study reveals that when high luminosity matter accretes onto a strongly magnetized neutron star, it forms a radiation pressure-dominated, magnetically confined accretion column. These columns are dynamically maintained through high-frequency oscillations of the accretion shock, which redistribute energy released at the shock through bulk vertical motions.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Review
Astronomy & Astrophysics
A. K. Srivastava, J. L. Ballester, P. S. Cally, M. Carlsson, M. Goossens, D. B. Jess, E. Khomenko, M. Mathioudakis, K. Murawski, T. V. Zaqarashvili
Summary: This review focuses on the importance of the chromosphere in mass and energy transport within the solar atmosphere. It discusses the physics of magnetohydrodynamic waves and instabilities in large-scale chromospheric structures and magnetic flux tubes, and also highlights key observational aspects that aid in understanding the role of the solar chromosphere in various dynamic processes and wave phenomena. Additionally, the heating scenario of the solar chromosphere is examined, along with potential implications, future trends, and outstanding questions in this field.
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
(2021)
Article
Astronomy & Astrophysics
Pallab Boro, Ram Prasad Prajapati
Summary: This study investigates the impact of galactic cosmic rays (CRs) on low-frequency magnetohydrodynamic (MHD) waves and linear gravitational instability in molecular clouds (MCs). It is found that CR diffusion affects the coupling of CR pressure-driven mode with dust-Alfven MHD mode and causes damping in the MHD waves. Furthermore, CR pressure stabilizes while CR diffusion destabilizes the growth rates of Jeans instability and significantly affects the gravitational collapse of dusty MCs.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
M. Changmai, J. M. Jenkins, J. B. Durrive, R. Keppens
Summary: This study uses high-resolution direct numerical simulations to investigate turbulent processes in solar prominences. The results show the presence of an anisotropic turbulence state with coherent structure formation predominantly in the vertical velocity component. Statistical analysis and higher-order structure functions confirm the consistency of the turbulence characteristics with previous observational studies.
ASTRONOMY & ASTROPHYSICS
(2023)
Article
Physics, Fluids & Plasmas
J. De Jonghe, N. Claes, R. Keppens
Summary: This research presents the extension of the open-source MHD spectroscopy code Legolas with viscosity and the Hall current, and benchmarks it against historic and recent findings. The results highlight the importance of these extensions for stability studies in dynamo experiments, protoplanetary disks, and magnetic reconnection.
JOURNAL OF PLASMA PHYSICS
(2022)
Article
Physics, Multidisciplinary
Jyoti Turi, A. P. Misra
Summary: This study examines the generation and instabilities of magnetohydrodynamic (MHD) waves in rotating plasmas in the galaxy, taking into account the effects of magnetic fields, self gravity, diffusion-convection of cosmic rays, and gas and cosmic-ray pressures. The coupling of different types of waves and their stability are significantly modified by the rotation and diffusion of cosmic fluids. The deviation of the rotation axis from the direction of the static magnetic field leads to coupling between Alfven waves and classical Jeans modes.
Article
Astronomy & Astrophysics
Peter B. Rau, Ira Wasserman
Summary: We investigated the stability of Hall magnetohydrodynamic with strong magnetic fields, focusing on the importance of Landau quantization of electrons. It was found that the strong-field Hall modes can become unstable due to the dependence of the differential magnetic susceptibility on magnetic field strength. The hydrodynamic instability, originating from thermodynamics and stabilized by magnetic domain formation, was analyzed using linear perturbation theory.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Peter B. Rau, Ira Wasserman
Summary: This study examines the magnetohydrodynamic stability of neutron star core matter under a strong magnetic field, finding that the magnetized fluid is unstable to a magnetosonic-type instability with growth times of the order of 10(-3) s under sufficiently strong magnetic field conditions. This instability is triggered by sharp changes in the second-order field derivative of the Lagrangian, influenced by Landau quantization of fermions and quantum electrodynamical effects.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
R. W. Dymott, A. J. Barker, C. A. Jones, S. M. Tobias
Summary: We investigate the linear and non-linear properties of the Goldreich-Schubert-Fricke (GSF) instability in stellar radiative zones with arbitrary local differential rotation. This instability may lead to turbulence that contributes to the redistribution of angular momentum and chemical composition in stars. Our analysis explores the effects of orientation of the shear with respect to the 'effective gravity' and the hydrodynamical evolution in three dimensions using a modified shearing box. This study provides insights into the transport properties of the GSF instability and its potential contribution to angular momentum transport in stars.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Physics, Fluids & Plasmas
D. Brunetti, J. P. Graves, C. J. Ham, S. Saarelma
Summary: This paper proposes a novel mechanism that explains the appearance of long-wavelength global instabilities in free boundary high-0 diverted tokamaks, which is strongly stabilized by the presence of a separatrix. By retrieving experimental observables in a dramatically simpler physical framework, this mechanism is shown to be more efficient than most models employed to describe such phenomena. The study demonstrates that the magnetohydrodynamic stability is affected by the synergy of 0 and plasma resistivity, with the wall effects significantly screened in an ideal plasma with separatrix. Toroidal flows can improve stability, depending on the proximity to the resistive marginal boundary. The analysis is performed in tokamak toroidal geometry, including averaged curvature and essential separatrix effects.
Article
Astronomy & Astrophysics
K. Mori, H. Hotta
Summary: In this work, we investigate the scale-dependent angular momentum flux using high-resolution three-dimensional magnetohydrodynamic simulations, without any manipulations, to reproduce solar-like differential rotation. We find that turbulence transports angular momentum radially inward, with a more pronounced effect at higher resolution. The dominant scale for the magnetic angular momentum transport is the smallest spatial scale. The high-resolution simulation shows low dimensionless magnetic correlation, indicating that chaotic yet strong small-scale magnetic fields achieve efficient magnetic angular momentum transport.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)