Relation between Growth Rate of the Suydam Mode and That of Low Mode Number Interchange Instability

1989 ◽  
Vol 58 (4) ◽  
pp. 1128-1130 ◽  
Author(s):  
Hideo Sugama ◽  
Masahiro Wakatani
Keyword(s):  
Growth Rate ◽  
Mode Number ◽  
Interchange Instability

Collisionless electrostatic interchange instabilities

1982 ◽  
Vol 28 (3) ◽  
pp. 551-564 ◽  
Author(s):  
S. Peter Gary ◽  
Michelle F. Thomsen
Keyword(s):  
Magnetic Field ◽  
Growth Rate ◽  
Dispersion Equation ◽  
Uniform Magnetic Field ◽  
Collisionless Plasma ◽  
Lower Hybrid ◽  
Plasma Instabilities ◽  
Weak Density ◽  
Interchange Instability ◽  
Kinetic Mode

The linear Vlasov dispersion equation for electrostatic plasma instabilities driven by gravity and weak density gradients perpendicular to a uniform magnetic field is derived and solved numerically. Two interchange instabilities emerge: the well-known fluid mode at long wavelengths and a kinetic mode at wavelengths short compared with the ion gyroradius. The properties of both instabilities are studied, as well as the effects of gravity on the universal and lower-hybrid density drift instabilities. The results show that the kinetic interchange generally has a larger growth rate than the fluid interchange instability, indicating that, whenever the latter is present in a collisionless plasma, the former may also be found.

scholarly journals Interchange instability of a curved current layerconvecting in the magnetosheath from the bow shock towards themagnetopause

2004 ◽  
Vol 22 (3) ◽  
pp. 993-999 ◽  
Author(s):  
I. L. Arshukova ◽  
N. V. Erkaev ◽  
H. K. Biernat
Keyword(s):  
Magnetic Field ◽  
Growth Rate ◽  
Solar Wind ◽  
Layer Structure ◽  
Dynamic Pressure ◽  
Bow Shock ◽  
Curvature Radius ◽  
Current Layer ◽  
Interchange Instability ◽  
The Magnetic Field

Abstract. This paper deals with nonsteady perturbations of the magnetosheath parameters which are related to variations of the interplanetary magnetic field from north to south under a constant solar wind dynamic pressure. The magnetic field changes its direction within a thin layer which is convected with the plasma from the bow shock to the ionopause. In the course of time, this current layer is amplified during its motion towards the magnetopause. The intensity of the current is increasing, the layer thickness is decreasing, and the gradients of parameters are becoming much sharper while the layer is approaching the magnetopause. The curvature radius of this layer is decreasing while it is draping around the magnetopause. This curved layer structure with reversed magnetic field in the magnetosheath is found to be unstable with respect to the interchange instability. The growth rate of the instability is obtained for different positions of the layer. Key words. Magnetospheric physics (magnetosheath)

scholarly journals Stabilization of the kinetic internal kink mode by a sheared poloidal flow

1999 ◽  
Vol 61 (4) ◽  
pp. 543-552 ◽  
Author(s):  
HIROSHI NAITOU ◽  
TOSHIMITSU KOBAYASHI ◽  
SHINJI TOKUDA
Keyword(s):  
Growth Rate ◽  
Skin Depth ◽  
Mode Number ◽  
Larmor Radius ◽  
Parameter Study ◽  
Pressure Gradients ◽  
Minor Radius ◽  
Kink Mode ◽  
Kinetic Effects ◽  
The Magnetic Field

The effects of a sheared poloidal flow on the m = 1 (poloidal mode number) and n = 1 (toroidal mode number) kinetic internal kink mode are simulated by the linearized version of the gyro-reduced MHD code, GRM3D-2F, based on a two-field and two-fluid gyro-reduced MHD model, including the kinetic effects of electron inertia and the perturbed electron pressure gradients along the magnetic field. A parameter study for different values of de (collisionless electron skin depth) with a fixed value of ρs = 0 (ion Larmor radius estimated by the electron temperature) shows that the smaller-de case, which has the smaller growth rate, is stabilized by the smaller sheared poloidal flow. When ρs is raised to ρs > de for a fixed value of de, the instability is stabilized by the smaller shear flow compared with the case of ρs < de, although the growth rate without the flow is larger for ρs > de. Since de is very much less than the minor radius, and ρs > de for the existing and future experiments, it is possible that even a quite small sheared poloidal flow may have a crucial influence on the kinetic internal kink mode.

The threshold energy for atom displacement in fcc metals

1990 ◽  
Vol 48 (4) ◽  
pp. 530-531
Author(s):  
Wilfried Sigle ◽  
Matthias Hohenstein ◽  
Alfred Seeger
Keyword(s):  
Growth Rate ◽  
Elevated Temperatures ◽  
Threshold Energy ◽  
Dislocation Loops ◽  
Absolute Minimum ◽  
Voltage Electron ◽  
Atom Displacement ◽  
Electron Microscopes ◽  
Fcc Metal

Prolonged electron irradiation of metals at elevated temperatures usually leads to the formation of large interstitial-type dislocation loops. The growth rate of the loops is proportional to the total cross-section for atom displacement,which is implicitly connected with the threshold energy for atom displacement, Ed . Thus, by measuring the growth rate as a function of the electron energy and the orientation of the specimen with respect to the electron beam, the anisotropy of Ed can be determined rather precisely. We have performed such experiments in situ in high-voltage electron microscopes on Ag and Au at 473K as a function of the orientation and on Au as a function of temperature at several fixed orientations.Whereas in Ag minima of Ed are found close to <100>,<110>, and <210> (13-18eV), (Fig.1) atom displacement in Au requires least energy along <100>(15-19eV) (Fig.2). Au is thus the first fcc metal in which the absolute minimum of the threshold energy has been established not to lie in or close to the <110> direction.

Saturation mechanism and generated viscosity in gravito-turbulent accretion disks

2020 ◽  
Vol 640 ◽  
pp. A53
Author(s):  
L. Löhnert ◽  
S. Krätschmer ◽  
A. G. Peeters
Keyword(s):  
Growth Rate ◽  
Numerical Simulations ◽  
Accretion Disks ◽  
Gravitational Instability ◽  
Turbulent Viscosity ◽  
Radial Distance ◽  
Maximum Growth ◽  
Wave Number ◽  
Radiative Cooling ◽  
Mixing Length

Here, we address the turbulent dynamics of the gravitational instability in accretion disks, retaining both radiative cooling and irradiation. Due to radiative cooling, the disk is unstable for all values of the Toomre parameter, and an accurate estimate of the maximum growth rate is derived analytically. A detailed study of the turbulent spectra shows a rapid decay with an azimuthal wave number stronger than ky−3, whereas the spectrum is more broad in the radial direction and shows a scaling in the range kx−3 to kx−2. The radial component of the radial velocity profile consists of a superposition of shocks of different heights, and is similar to that found in Burgers’ turbulence. Assuming saturation occurs through nonlinear wave steepening leading to shock formation, we developed a mixing-length model in which the typical length scale is related to the average radial distance between shocks. Furthermore, since the numerical simulations show that linear drive is necessary in order to sustain turbulence, we used the growth rate of the most unstable mode to estimate the typical timescale. The mixing-length model that was obtained agrees well with numerical simulations. The model gives an analytic expression for the turbulent viscosity as a function of the Toomre parameter and cooling time. It predicts that relevant values of α = 10−3 can be obtained in disks that have a Toomre parameter as high as Q ≈ 10.

TEMPERATURE DEPENDENCE OF THE CRYSTAL GROWTH RATE IN POLAR GLACIERS

1987 ◽  
Vol 48 (C1) ◽  
pp. C1-661-C1-662 ◽  
Author(s):  
J. R. PETIT ◽  
P. DUVAL ◽  
C. LORIUS
Keyword(s):  
Growth Rate ◽  
Crystal Growth ◽  
Temperature Dependence ◽  
Crystal Growth Rate

Forming Sources of Long-run Growth: How to Understand Them?

2014 ◽  
pp. 4-20 ◽  
Author(s):  
G. Idrisov ◽  
S. Sinelnikov-Murylev
Keyword(s):  
Economic Growth ◽  
Growth Rate ◽  
Economic Policy ◽  
Business Cycle ◽  
Capital Markets ◽  
Productivity Growth ◽  
Government Spending ◽  
Long Run ◽  
Accelerate Growth ◽  
Budget Institutions

The paper analyzes the inconsequence and problems of Russian economic policy to accelerate economic growth. The authors consider three components of growth rate (potential, Russian business cycle and world business cycle components) and conclude that in order to pursue an effective economic policy to accelerate growth, it has to be addressed to the potential (long-run) growth component. The main ingredients of this policy are government spending restructuring and budget institutions reform, labor and capital markets reforms, productivity growth.

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