Stability of a system with cosmic rays and waves

Lo, Yu-Tsung; Ko, C. M.

doi:10.1051/0004-6361:20066938

Cited by 5 publications

(8 citation statements)

References 34 publications

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“…The downstream regions of the quasi-uniform-flowtype solution are stable. This is consistent with the result of Lo & Ko (2007), which considered a system with a prescribed uniform flow. In contrast, the downstream regions of the modified-shocktype solution are unstable.…”

Section: An Examplesupporting

confidence: 91%

“…In the reduced system where the background plasma flow is not perturbed, Lo & Ko (2007) found that the instability is due to stochastic acceleration. Since stochastic acceleration is absent in unidirectional wave systems, we might expect that they should be less susceptible to the instability than the twowave systems.…”

Section: Summary and Discussionmentioning

confidence: 99%

“…Lo & Ko (2007) found that the system is stable in the very short wavelength limit, and also in the limit of e − 1, e + 1, or e c 1. The instability is caused by the stochastic acceleration.…”

Section: Perpendicular Perturbations (μ = 0)mentioning

confidence: 99%

“…The cosmic-ray-MHD system reduces to a threefluid model, which comprises cosmic ray and two self-excited Alfvén waves only (see Jiang et al 1996;Ko 1998). Lo & Ko (2007) studied the stability of such systems. In fact, the dispersion relation is just…”

Section: Perpendicular Perturbations (μ = 0)mentioning

confidence: 99%

“…To the best of our knowledge, the only study on the stability of the cosmic-ray-MHD system in a background with both forward and backward Alfvén waves is Lo & Ko (2007). The system considered was a reduced one in which the thermal plasma flow was immune to perturbation.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Stability of a Cosmic-Ray-Magnetohydrodynamic System

2009

ApJ

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We study the stability of a four-fluid cosmic-ray-MHD system which comprises magnetized thermal plasma, cosmic rays, forward and backward propagating Alfvén waves. The coupling between the plasma, cosmic rays, and waves depends on the energy density of the waves. Local short-wavelength small perturbation analysis is performed on a background steady state. The magnetoacoustic modes of the plasma are modified and intertwined with cosmic ray and wave modes, while the plasma Alfvén mode is unaffected. The parameter space is large and the stable/unstable regions of the system are complicated. We discuss some special cases analytically and work out some general cases numerically. Roughly speaking, the system is more likely to be stable if the perturbations have very short wavelength, not propagating at large angle with background magnetic field, large cosmic ray energy density, not too small energy density for both waves and large thermal energy density (and no self-gravity).

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Section: An Examplesupporting

confidence: 91%

Section: Summary and Discussionmentioning

confidence: 99%

Section: Perpendicular Perturbations (μ = 0)mentioning

confidence: 99%

Section: Perpendicular Perturbations (μ = 0)mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Stability of a Cosmic-Ray-Magnetohydrodynamic System

2009

ApJ

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Magneto-rotational instability with the effect of cosmic rays

Kuwabara

2015

Proc. IAU

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We present the results obtained from linear stability analysis and 2.5dimensional magnetohydrodynamic (MHD) simulations of the magnetorotational instability (MRI), including the effects of cosmic rays (CRs). We took into account of the CR diffusion along the magnetic field but neglect the cross-field-line diffusion. Two models are considered in this paper: shearing box model and differentially rotating cylinder model. We studied how MRI is affected by the initial CR pressure (i.e., energy) distribution. In the shearing box model, the initial state is uniform distribution. Linear analysis shows that the growth rate of MRI does not depend on the value of CR diffusion coefficient. In the differentially rotating cylinder model, the initial state is a constant angular momentum polytropic disk threaded by weak uniform vertical magnetic field. Linear analysis shows that the growth rate of MRI becomes larger if the CR diffusion coefficient is larger. Both results are confirmed by MHD simulations. The MHD simulation results show that the outward movement of matter by the growth of MRI is not impeded by the CR pressure gradient, and the centrifugal force which acts to the concentrated matter becomes larger. Consequently, the growth rate of MRI is increased. On the other hand, if the initial CR pressure is uniform, then the growth rate of the MRI barely depends on the value of the CR diffusion coefficient.

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Analysis of Magnetorotational Instability With the Effect of Cosmic-Ray Diffusion

Kuwabara

2014

ApJ

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We present the results obtained from the linear stability analysis and 2.5 dimensional magnetohydrodynamic (MHD) simulations of magnetorotational instability (MRI), including the effects of cosmic rays (CRs). We took into account the CR diffusion along the magnetic field but neglected the cross-field-line diffusion. Two models are considered in this paper: the shearing box model and differentially rotating cylinder model. We studied how MRI is affected by the initial CR pressure (i.e., energy) distribution. In the shearing box model, the initial state is uniform distribution. Linear analysis shows that the growth rate of MRI does not depend on the value of the CR diffusion coefficient. In the differentially rotating cylinder model, the initial state is a constant angular momentum polytropic disk threaded by a weak uniform vertical magnetic field. Linear analysis shows that the growth rate of MRI becomes larger if the CR diffusion coefficient is larger. Both results are confirmed by MHD simulations. The MHD simulation results show that the outward movement of matter by the growth of MRI is not impeded by the CR pressure gradient, and the centrifugal force that acts on the concentrated matter becomes larger. Consequently, the growth rate of MRI is increased. On the other hand, if the initial CR pressure is uniform, then the growth rate of the MRI barely depends on the value of the CR diffusion coefficient.

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Stability of a system with cosmic rays and waves

Cited by 5 publications

References 34 publications

Stability of a Cosmic-Ray-Magnetohydrodynamic System

Stability of a Cosmic-Ray-Magnetohydrodynamic System

Magneto-rotational instability with the effect of cosmic rays

Analysis of Magnetorotational Instability With the Effect of Cosmic-Ray Diffusion

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