搜索结果: 1-15 共查到“天文学 Instability”相关记录28条 . 查询时间(0.476 秒)
Gravitational instability and clustering in a disk of planetesimals
stars planetary systems protoplanetary disks – gravitation – planets satellites formation
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2015/12/25
For a long time, gravitational instability in the disk of planetesimals has been suspected to be the main engine responsible for the beginning of dust growth, its advantage being that it provides forr...
Vibrational Instability of Metal-Poor Low-Mass Main-Sequence Stars
Vibrational Instability Metal-Poor Low-Mass Main-Sequence Stars
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2012/2/24
We find that low-degree low-order g-modes become unstable in metal-poor low-mass stars due to the $\varepsilon$-mechanism of the pp-chain. Since the outer convection zone of these stars is limited onl...
Large-scale magnetic field generation via the Kelvin-Helmholtz instability
Large-scale magnetic field generation Kelvin-Helmholtz instability
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2011/10/18
We present the first self-consistent three-dimensional particle-in-cell simulations of the Kelvin-Helmholtz instability (KHI) in an unmagnetized scenario. We discuss the main features, including densi...
A long-wavelength instability involving the stress tensor
instabilities—cosmic rays—acceleration of particles—ISM: supernova remnants
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2011/10/20
Cosmic ray acceleration through first-order Fermi acceleration in a collisionless plasma relies on efficient scattering off magnetic field fluctuations. Scattering is most efficient for magnetic field...
The Kelvin-Helmholtz instability in weakly ionised plasmas: Ambipolar dominated and Hall dominated flows
mhd – instabilities – ISM:clouds – ISM:kinematics and dynamics
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2011/10/12
The Kelvin-Helmholtz instability is well known to be capable of converting well-ordered flows into more disordered, even turbulent, flows. As such it could represent a path by which the energy in, for...
Gravitational instability of the primordial plasma: anisotropic evolution of structure seeds
Gravitational instability primordial plasma: anisotropic evolution
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2011/10/10
We study how the presence of a background magnetic field, of intensity compatible with current observation constraints, affects the linear evolution of cosmological density perturbations at scales bel...
Magnetorotational Instability Driven Accretion in Protoplanetary Disks
Instability Driven Accretion Protoplanetary
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2011/10/9
The gas dynamics in protoplanetary disks (PPDs) is strongly affected by non-ideal MHD effects. Using a complex chemical reaction network with standard prescriptions for X-ray and cosmic-ray ionization...
Properties of the negative effective magnetic pressure instability
magnetohydrodynamics (MHD) – instabilities – turbulence
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2011/10/9
As was demonstrated in earlier studies, turbulence can result in a negative contribution to the effective mean magnetic pressure, which, in turn, can cause a large-scale instability. In this study, hy...
Analysis of 3D MHD Instability of Antisolar Latitudinal Differential Rotation in F, G and K stars
Analysis Instability Latitudinal Differential Rotation
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2011/10/8
Motivated by observations that only a very few stars have been found to have antisolar differential rotation, much weaker in amplitude than that of the Sun, we analyze the stability of antisolar and s...
Black Hole growth and AGN obscuration by instability-driven inflows in high-redshift disk galaxies fed by cold streams
instability-driven inflows high-redshift disk galaxies cold streams
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2011/9/29
Disk galaxies at high redshift have been predicted to maintain high gas surface densities due to continuous feeding by intense cold streams leading to violent gravitational instability, transient feat...
Giant Planet Formation by Disk Instability in Low Mass Disks?
Giant Planet Formation Disk Instability Low Mass Disks
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2011/1/11
Forming giant planets by disk instability requires a gaseous disk that is massive enough to become gravitationally unstable and able to cool fast enough for self-gravitating clumps to form and survive...
Revisiting the Flowers-Ruderman instability of magnetic stars
magnetic fields MHD – stars magnetic field
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2010/11/10
In 1977, Flowers and Ruderman described a perturbation that destabilises a purely
dipolar magnetic field in a fluid star. They considered the effect of cutting the star
in half along a plane contain...
Magnetic fields of Ap stars as a result of an instability
Stars chemically peculiar magnetic fields – instabilities
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2010/11/15
Ap star magnetism is often attributed to fossil magnetic fields which have not changed much since the pre-main-sequence epoch of the stars. Stable magnetic field configurations are known which could p...
MHD Simulations of Parker Instability Undergoing Cosmic-Ray Diffusion: Effect of the Initial Equilibrium Conditions on Mixing
cosmic rays magnetohydrodynamics instability numerical simulation
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2010/11/9
Parker instability arises from the presence of magnetic fields in a plasma such as the interstellar medium (ISM),wherein the magnetic buoyant pressure expels the gas and causes the gas to move along t...
Alpha effect due to buoyancy instability of a magnetic layer
magnetohydrodynamics Sun: magnetic fields Instabilities Turbulence Sun dynamo
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2010/11/11
Context. A strong toroidal field can exist in form of a magnetic layer in the overshoot region below the solar convection zone. This motivates a more detailed study of the magnetic buoyancy instabilit...