ON THE OSCILLATIONS OF A WEAKLY INHOMOGENEOUS PLASMA

1965 ◽  
Vol 43 (4) ◽  
pp. 640-644
Author(s):  
Som Krishan
Keyword(s):  
Magnetic Field ◽  
Growth Rate ◽  
Wave Vector ◽  
Inhomogeneous Plasma ◽  
Collisionless Plasma ◽  
Velocity Distribution Function ◽  
One Dimension ◽  
Larmor Radius ◽  
Small Inhomogeneity ◽  
Inhomogeneity Parameter

Oscillations of a collisionless plasma in equilibrium with a magnetic field which is weakly inhomogeneous in one dimension are studied. The calculations are based on longitudinal oscillations, i.e. the electric vector is parallel to the wave vector. The procedure employed is to use Maxwell's equations and expand the velocity distribution function about its equilibrium value for finding the perturbation in the distribution. The dispersion relation so obtained is different from that of Rosenbluth et al. (1962). The system is stable for the small Landau growth rate (Landau 1946), which might become appreciable for wavelengths comparable with the Larmor radius, provided [Formula: see text], where k is the wave vector and ε is a small inhomogeneity parameter.

Electron whistler mode instability in an inhomogeneous thermal plasma in the presence of an inhomogeneous beam of suprathermal electrons

1983 ◽  
Vol 29 (3) ◽  
pp. 439-448 ◽  
Author(s):  
H.A. Shah ◽  
V.K. Jain
Keyword(s):  
Magnetic Field ◽  
Growth Rate ◽  
Dispersion Relation ◽  
Thermal Plasma ◽  
Uniform Magnetic Field ◽  
Inhomogeneous Plasma ◽  
Mode Instability ◽  
Whistler Mode ◽  
Suprathermal Electrons ◽  
Whistler Mode Waves

The excitation of the whistler mode waves propagating obliquely to the constant and uniform magnetic field in a warm and inhomogeneous plasma in the presence of an inhomogeneous beam of suprathermal electrons is studied. The full dispersion relation including electromagnetic effects is derived. In the electrostatic limit the expression for the growth rate is given. It is found that the inhomogeneities in both beam and plasma number densities affect the growth rates of the instabilities.

Effect of Finite Larmor Radius on the Rayleigh-Taylor Instability of Two Component Magnetized Rotating Plasma

1998 ◽  
Vol 53 (12) ◽  
pp. 937-944 ◽  
Author(s):  
P. K. Sharma ◽  
R. K. Chhajlani
Keyword(s):  
Magnetic Field ◽  
Growth Rate ◽  
Normal Mode Analysis ◽  
Mode Analysis ◽  
Larmor Radius ◽  
Horizontal Magnetic Field ◽  
Finite Larmor Radius ◽  
Neutral Particles ◽  
Rayleigh Taylor Instability ◽  
Superposed Fluids

Abstract The Rayleigh-Taylor (R-T) instability of two superposed plasmas, consisting of interacting ions and neutrals, in a horizontal magnetic field is investigated. The usual magnetohydrodynamic equations, including the permeability of the medium, are modified for finite Larmor radius (FLR) corrections. From the relevant linearized perturbation equations, using normal mode analysis, the dispersion relation for the two superposed fluids of different densities is derived. This relation shows that the growth rate unstability is reduced due to FLR corrections, rotation and the presence of neutrals. The horizontal magnetic field plays no role in the R-T instability. The R-T instability is discussed for various simplified configurations. It remains unaffected by the permeability of the porous medium, presence of neutral particles and rotation. The effect of different factors on the growth rate of R-T instability is investigated using numerical analysis. Corresponding graphs are plotted for showing the effect of these factors on the growth of the R-T instability.

Stimulated backscattering of electromagnetic ordinary waves from extraordinary waves below the upper hybrid frequency

1979 ◽  
Vol 21 (1) ◽  
pp. 97-106 ◽  
Author(s):  
Behrooz Maraghechi ◽  
Joseph E. Willett
Keyword(s):  
Magnetic Field ◽  
Growth Rate ◽  
Static Magnetic Field ◽  
Inhomogeneous Plasma ◽  
Extraordinary Wave ◽  
Threshold Power ◽  
Ordinary Wave ◽  
Homogeneous Plasma ◽  
Parametric Decay ◽  
Hybrid Frequency

The parametric decay of an intense electromagnetic ordinary wave, propagating perpendicular to a uniform static magnetic field, into an extraordinary wave and a backscattered ordinary wave is investigated. Formulae are derived for the growth rate and threshold power associated with the instability in a homogeneous plasma. An analysis of the spatial amplification of the decay waves in an inhomogeneous plasma is presented. The effects of the uniform static magnetic field on the backscattering in both homogeneous and inhomogeneous plasmas are studied numerically.

Filamentation instability of a laser beam in an inhomogeneous plasma in an arbitrarily oriented external magnetic field

2013 ◽  
Vol 79 (5) ◽  
pp. 921-926
Author(s):  
A. HASANBEIGI ◽  
A. MOUSAVI ◽  
H. MEHDIAN
Keyword(s):  
Magnetic Field ◽  
Growth Rate ◽  
External Magnetic Field ◽  
Laser Beam ◽  
Short Pulse ◽  
Inhomogeneous Plasma ◽  
Plasma Inhomogeneity ◽  
Short Pulse Laser ◽  
Filamentation Instability ◽  
Applied External Magnetic Field

AbstractThe interaction of a short pulse laser beam with an inhomogeneous plasma has been studied in the presence of an obliquely applied external magnetic field. The dispersion relation and the analytical growth rate have been obtained solving the nonlinear wave equation. It is found that the growth rate and the cut-off wavenumber are strongly influenced by the direction and magnitude of the applied magnetic field. Moreover, the growth rate has been modified by plasma inhomogeneity.

Evolution of nonlinear magnetosonic waves propagating obliquely to an external magnetic field in a collisionless plasma

2000 ◽  
Vol 64 (3) ◽  
pp. 211-226 ◽  
Author(s):  
DEBALINA CHAKRABORTY ◽  
K. P. DAS
Keyword(s):  
Magnetic Field ◽  
Hall Current ◽  
Collisionless Plasma ◽  
Momentum Equation ◽  
Finite Amplitude ◽  
Larmor Radius ◽  
Finite Larmor Radius ◽  
Petviashvili Equation ◽  
Flr Effects ◽  
External Uniform Magnetic Field

It is shown that the asymptotic evolution of finite-amplitude magnetosonic waves propagating obliquely to an external uniform magnetic field in a warm homogeneous plasma is governed by a Kadomtsev–Petviashvili equation having an extra dispersive term. The dispersion is provided by finite-Larmor-radius (FLR) effects in the momentum equation and by the Hall-current and electron-pressure corrections in the generalized Ohm's law. A double-layer-type solution of the equation is obtained, and the equation is shown to reduce to a KdV–Burgers equation under certain assumptions.

Longitudinal waves in a perpendicular collisionless plasma shock: I. Cold ions

1970 ◽  
Vol 4 (4) ◽  
pp. 739-751 ◽  
Author(s):  
S. Peter Gary ◽  
J. J. Sanderson
Keyword(s):  
Magnetic Field ◽  
Growth Rate ◽  
Collisionless Plasma ◽  
Maximum Growth ◽  
Maximum Growth Rate ◽  
Wave Number ◽  
Zero Magnetic Field ◽  
Linear Dispersion ◽  
Electrostatic Waves ◽  
Cold Ions

This paper considers electrostatic waves in a Vlasov plasma of unmagnetized ions and magnetized, Maxwellian electrons. The linear dispersion relation is derived for waves in a perpendicular shock such that the most important sources of instability are the E × B and ∇B electron drifts. For the case of cold ions, propagation perpendicular to the applied magnetic field, and the E × B drift alone, a numerical analysis of frequency vs. wave-number is presented. The effects of the ∇B drift are also considered, and it is shown that the maximum growth rate can be larger than the maximum growth rate for the zero magnetic field ion acoustic instabifity under comparable conditions.

Current driven electromagnetic ion cyclotron instability

1979 ◽  
Vol 21 (1) ◽  
pp. 127-139 ◽  
Author(s):  
D. W. Forslund ◽  
J. M. Kindel ◽  
M. A. Stroscio
Keyword(s):  
Magnetic Field ◽  
Drift Velocity ◽  
Electron Distribution ◽  
Collisionless Plasma ◽  
Larmor Radius ◽  
Electron Drift ◽  
Thermal Velocity ◽  
Plasma Parameters ◽  
Cyclotron Instability ◽  
Ion Cyclotron

When an electron distribution drifts relative to the ions along a d.c. magnetic field, it is known that, above some critical drift velocity, a nearly field-aligned electromagnetic ion cyclotron instability may be excited. We extend the study of this instability over wide variations in plasma parameters, ion β in particular, and beyond marginal stability.Above threshold the most unstable waves propagate very obliquely to the ambient d.c. magnetic field at wavenumbers of the order of an inverse ion Larmor radius. At low ion β the critical electron drift normalized to the ion thermal velocity scales inversely as β i- ½ while, for β i>10-2, the critical drift scales as the ion thermal velocity. For the Te≈Tielectromagnetic ion cyclotron instabifity begins to have a lower threshold than the corresponding electrostatic instability at β i≈me/Mi. In a moderately high β i, homogeneous, collisionless plasma the electromagnetic ion cyclotron instability appears to have the lowest threshold of any current driven instability.

Evolution of nonlinear Alfvén waves propagating along the magnetic field in a collisionless plasma

1982 ◽  
Vol 28 (3) ◽  
pp. 459-468 ◽  
Author(s):  
M. Khanna ◽  
R. Rajaram
Keyword(s):  
Magnetic Field ◽  
Collisionless Plasma ◽  
Momentum Equation ◽  
Finite Amplitude ◽  
Alfven Wave ◽  
Mhd Waves ◽  
Larmor Radius ◽  
Finite Larmor Radius ◽  
Flr Effects ◽  
The Magnetic Field

It is shown that the asymptotic evolution of a finite-amplitude Alfvén wave propagating parallel to the uniform magnetic field in a warm homogeneous collisionless plasma is governed by the modified nonlinear Schrödinger equation. The dispersion is provided by the ion finite Larmor radius (FLR) effects in the momentum equation and the Hall current and electron pressure corrections to the generalized Ohm's law. In the cold plasma limit the equations reduce to those available in the literature. It is suggested that these calculations can have a bearing on the investigation of the structure of MHD waves in the solar wind.

On the generation of magnetic fields due to ponderomotive forces in astrophysical plasmas

2002 ◽  
Vol 67 (2-3) ◽  
pp. 129-138 ◽  
Author(s):  
A. ROY CHOWDHURY ◽  
M. KHURSHED ALAM ◽  
K. ROY CHOWDHURY ◽  
S. N. PAUL ◽  
B. A. BEGUM
Keyword(s):  
Magnetic Field ◽  
Growth Rate ◽  
Magnetic Fields ◽  
Electromagnetic Waves ◽  
Inhomogeneous Plasma ◽  
Astrophysical Plasma ◽  
Astrophysical Plasmas ◽  
Ponderomotive Forces ◽  
Collisional Interactions ◽  
The Magnetic Field

The generation of magnetic fields due to ponderomotive forces in astrophysical plasma consisting of electrons, ions and positrons is investigated theoretically. It is seen that collisional or non-collisional interactions (between electromagnetic waves and plasma particles) via ponderomotive forces in an inhomogeneous plasma can excite a magnetic field. The growth rate of the magnetic field is illustrated graphically for different values of the temperature and concentration of positrons in the plasma.

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.

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