The Stability of a Self-Gravitating Nonrotating Gas Layer with Stellar, Magnetic, and Cosmic-Ray Components. 11.

1973 ◽  
Vol 179 ◽  
pp. 103 ◽  
Author(s):  
Sanford A. Kellman
Keyword(s):  
Cosmic Ray ◽  
The Stability ◽  
Gas Layer

scholarly journals Cosmic ray tracking to monitor the stability of historical buildings: a feasibility study

2019 ◽  
Vol 30 (4) ◽  
pp. 045901 ◽  
Author(s):  
G Bonomi ◽  
M Caccia ◽  
A Donzella ◽  
D Pagano ◽  
V Villa ◽  
...  
Keyword(s):  
Feasibility Study ◽  
Cosmic Ray ◽  
Historical Buildings ◽  
The Stability

The stability of cosmic-ray-dominated shocks - A secondary instability

1993 ◽  
Vol 405 ◽  
pp. 199 ◽  
Author(s):  
Dongsu Ryu ◽  
Hyesung Kang ◽  
T. W. Jones
Keyword(s):  
Cosmic Ray ◽  
Secondary Instability ◽  
The Stability

A cosmic-ray-driven plasma instability

1989 ◽  
Vol 41 (1) ◽  
pp. 89-95 ◽  
Author(s):  
G. P. Zank
Keyword(s):  
Magnetic Field ◽  
Cosmic Rays ◽  
Thermal Plasma ◽  
Cosmic Ray ◽  
Mhd Equations ◽  
Mutual Interaction ◽  
Shock Acceleration ◽  
Wave Effects ◽  
The Stability

The stability of the MHD equations describing the mutual interaction of cosmic rays, thermal plasma, magnetic field and Alfvén waves used in cosmic-ray-shock acceleration theory (e.g. McKenzie & Völk 1982) is analysed for linear compressive instabilities. It is found that the inclusion of wave effects implies that the forward propagating sub-Alfvénic mode is unstable on wavelength scales greater than 1 parsec. The role of the instability in astrophysical models is considered.

The interaction of long-wavelength compressive waves with a cosmic ray shock

1987 ◽  
Vol 37 (3) ◽  
pp. 363-372 ◽  
Author(s):  
G. P. Zank ◽  
J. F. Mckenzie
Keyword(s):  
Dispersion Equation ◽  
Transmission Coefficient ◽  
Cosmic Ray ◽  
Long Wavelength ◽  
The Stability ◽  
Two Fluid

This paper investigates the stability of a cosmic ray shock to long-wavelength perturbations. The problem is formulated in terms of finding the transmission coefficient for compressive waves across a cosmic ray shock by solving the generalized, two-fluid Rankine-Hugoniot relations. For strong shocks, the transmission coefficient confirms that compressive waves can undergo considerable amplification on passage through such shocks. The resonances of the transmission coefficient provides us with the dispersion equation governing the stability of the shock to long-wavelength ripple-like distortions. By using the principle of the argument method, it is established that cosmic ray shocks are stable.

Stability Analysis of Cassie-Baxter State Under Pressure Driven Flow

2010 ◽  
Author(s):  
Tae Jin Kim ◽  
Carlos H. Hidrovo
Keyword(s):  
Liquid Layer ◽  
Friction Reduction ◽  
Wetting Transition ◽  
Textured Surface ◽  
Microchannel Flow ◽  
Flow Conditions ◽  
Cassie State ◽  
The Stability ◽  
Gas Layer ◽  
Micro Cavity

The Cassie-Baxter state is a phenomenon in which a liquid rests on top of a textured surface with a gas layer trapped underneath the liquid layer. This gas layer introduces an effective shear free boundary that induces slip at the liquid-gas interface, allowing for friction reduction in liquid channel flows. Multiple studies have shown that different surface configurations result in different friction reduction characteristics, and most work is aimed at controlling the roughness factor and its shape in order to achieve an increased slip flow. This paper investigates the effects that different texturing geometries have on the stability of the Cassie state under pressurized microchannel flow conditions. To test the stability effects associated with the pressurized microchannel flow conditions, microfluidic channels with microstructures on the side walls were designed and fabricated. The microstructures were designed to induce the Cassie state with a liquid-air interface forming between the texturing trenches. The air trapped within the microstructure is treated as an ideal gas, with the compressibility induced pressure rise acting as a restrictive force against the Wenzel wetting transition. The model was validated against experimental flow data obtained using microchannel samples with microtextured boundaries. The microchannels were fabricated in PDMS (poly-dimethylsiloxane) using soft lithography and were baked on a hot plate to ensure the hydrophobicity of the microtexture. Pressure versus flow rate data was obtained using a constant gravitational pressure head setup and a flow meter. The liquid-gas interface layer in the microchannel was visualized using bright field microscopy that allowed measurement of the liquid penetration depth into the microtexturing throughout the microhannel. The experimental results indicate that air trapped in the pockets created by micro-cavity structures prevented the liquid layer from completely filling the void. As expected, the pressure drop in the micro-cavity textured channel showed a considerable decrease compared to that in the flat surfaced channel. These results also suggest that micro-cavities can maintain the Cassie state of a liquid meniscus, resting on top of the surface, in larger pressure ranges than open spaced micro-pillars arrays.

Short-wavelength compressive instabilities in cosmic ray shocks and heat conduction flows

1987 ◽  
Vol 37 (3) ◽  
pp. 347-361 ◽  
Author(s):  
G. P. Zank ◽  
J. F. Mckenzie
Keyword(s):  
Solar Wind ◽  
Heat Conduction ◽  
Cosmic Ray ◽  
Theoretical Models ◽  
Dissipative Heating ◽  
Wave Action ◽  
Background Flow ◽  
Wave Amplification ◽  
Shock Transition ◽  
The Stability

In this paper we discuss the stability of three genetically similar non-uniform flows to compressive disturbances whose wavelengths are much shorter than the length scales characterizing the background flow. The results are relevant to theoretical models of cosmic ray shocks and solar wind type flows involving heat conduction. A JWKB expansion solution yields an equation which determines how the amplitudes of the perturbations may grow (or decay) as they propagate within such structures. It is shown that, in all three of the models considered, the perturbations exhibit spatial growth if the background flow is sufficiently supersonic and decelerating. The associated equations describing the evolution of the wave action are also studied with a view to deciding whether or not the behaviour of this attractive variable can provide an unambiguous answer to the question of stability. In the case of a shock transition dominated by heat conduction, it is shown that the effects of dissipative heating within the transition more than offset those of wave growth, with the result that wave amplification is accompanied by wave action decay. Therefore in general it would appear that the wave action equation alone cannot unambiguously settle stability questions.

On the stability of cosmic ray dominated shocks

1992 ◽  
Author(s):  
Hyesung Kang ◽  
Dongsu Ryu ◽  
T. W. Jones
Keyword(s):  
Cosmic Ray ◽  
The Stability

scholarly journals Cosmic Rays and the Parker Instability

1985 ◽  
Vol 107 ◽  
pp. 361-363
Author(s):  
A.H. Nelson
Keyword(s):  
Magnetic Field ◽  
Cosmic Rays ◽  
Interstellar Medium ◽  
Galactic Halo ◽  
Cosmic Ray ◽  
Interstellar Gas ◽  
Horizontal Magnetic Field ◽  
Magnetic Buoyancy ◽  
Field Lines ◽  
Gas Layer

Parker (1966, 1969, 1979) has shown that the magnetic buoyancy of a uniform horizontal magnetic field will destabilize the Galactic gas layer. Perturbations of the form shown in Fig. 1 will grow in time with the magnetic loops ballooning up into the Galactic halo, and the interstellar gas draining down the field lines to collect in the mid-plane. Parker also showed that if the dynamical effect of the cosmic ray component of the interstellar medium is included, using an isotropic cosmic ray pressure, then the instability is enhanced.

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