scholarly journals General Dispersion Relation for Surface Waves on a Plasma?Vacuum Interface: Application to Magnetised Plasmas

1992 ◽  
Vol 45 (1) ◽  
pp. 55 ◽  
Author(s):  
GW Rowe
Keyword(s):  
Dispersion Relation ◽  
General Theory ◽  
Surface Waves ◽  
Low Frequency ◽  
Surface Currents ◽  
Ion Plasma ◽  
Vacuum Interface ◽  
Slight Extension ◽  
Infinite Conductivity ◽  
General Dispersion

The general dispersion relation for electromagnetic surface waves on a plasma-vacuum interface, recently derived by Rowe (1991), is applied to the case of a cold magnetised plasma bounded by a vacuum. It is illustrated how the dispersion relation and the surface wave fields may be determined in practice, and some general results are given. It is remarked that a plasma of this type satisfies the consistency conditions which were derived for the general theory by Rowe. These general results are then used to reproduce the dispersion relation of Cramer and Donnelly (1983) for low frequency surface waves in an electron-ion plasma. This example illustrates the general principles of the theory. A major difference between the derivation in their paper and the calculation of this paper is that in the former the plasma was assumed to be infinitely conducting whereas here the plasma is strictly assumed to have finite conductivity.The transition to infinite conductivity, which involves a slight extension of the general theory to include surface currents, is thus also discussed.

Surface waves on the inhomogeneous interface between radiative electron–ion plasma and vacuum

2021 ◽  
Vol 87 (4) ◽  
Author(s):  
N. Maryam ◽  
Ch. Rozina ◽  
B. Arooj ◽  
A. Asma ◽  
I. Kourakis
Keyword(s):  
Dispersion Relation ◽  
Surface Waves ◽  
Energy Balance Equation ◽  
Surface Instability ◽  
Temperature Inhomogeneity ◽  
Magnetic Field Effects ◽  
Surface Mass ◽  
Ion Plasma ◽  
Vacuum Interface ◽  
The Impact

The impact of temperature inhomogeneity, surface charge and surface mass densities on the stability analysis of charged surface waves at the interface between dense, incompressible, radiative, self-gravitating magnetized electron–ion plasma and vacuum is investigated. For such an incompressible plasma system, the temperature inhomogeneity is governed by an energy balance equation. Adopting the one-fluid magnetohydrodynamic (MHD) approximation, a general dispersion relation is obtained for capillary surface waves, which takes into account gravitational, radiative and magnetic field effects. The dispersion relation is analysed to obtain the conditions under which the plasma–vacuum interface may become unstable. In the absence of electromagnetic (EM) pressure, astrophysical objects undergo gravitational collapse through Jeans surface oscillations in contrast to the usual central contraction of massive objects due to enhanced gravity. EM radiation does not affect the dispersion relation much, but actually tends to stabilize the Jeans surface instability. In certain particular cases, pure gravitational radiation may propagate on the plasma vacuum interface. The growth rate of radiative dissipative instability is obtained in terms of the wavevector. Our theoretical model of the Jeans surface instability is applicable in astrophysical environments and also in laboratory plasmas.

General dispersion relation for surface waves on a plasma—vacuum interface: an image approach

1991 ◽  
Vol 46 (3) ◽  
pp. 495-511 ◽  
Author(s):  
G. W. Rowe
Keyword(s):  
Dispersion Relation ◽  
Boundary Conditions ◽  
Surface Waves ◽  
Image Theory ◽  
Magnetic Medium ◽  
Vacuum Interface ◽  
General Dispersion ◽  
Unmagnetized Plasma ◽  
Special Case ◽  
Plane Plasma

The image approach, used extensively to treat bounded unmagnetized plasmas, is extended to the case of an arbitrary homogeneous and non-magnetic medium. A general dispersion relation for electromagnetic surface waves on a plane plasma-vacuum interface is thus obtained, subject only to the suitability of the chosen boundary conditions. The boundary conditions used here are those of Barr and Boyd. It is emphasized that this dispersion relation is applicable to magnetized plasmas. The general dispersion relation is applied to the special case of an isotropie medium, and the dispersion relation of Barr and Boyd for an unmagnetized plasma is reproduced. A major assumption in the image approach is that the semi-infinite bounded medium can be described by the infinite-medium response. The validity of this assumption and of the boundary conditions is discussed. Two conditions are deduced that must be satisfied for the image theory to be self-consistent. It is argued that these can be satisfied in all situations for which the assumed boundary conditions are appropriate.

Ion-cyclotron modes in weakly relativistic plasmas

1994 ◽  
Vol 51 (3) ◽  
pp. 371-379 ◽  
Author(s):  
Chandu Venugopal ◽  
P. J. Kurian ◽  
G. Renuka
Keyword(s):  
Dispersion Relation ◽  
High Frequency ◽  
Low Frequency ◽  
Dispersion Relations ◽  
The Other ◽  
Larmor Radius ◽  
Relativistic Plasmas ◽  
Ion Plasma ◽  
Maxwellian Plasma ◽  
Relativistic Dispersion

We derive a dispersion relation for the perpendicular propagation of ioncyclotron waves around the ion gyrofrequency ω+ in a weaklu relaticistic anisotropic Maxwellian plasma. These waves, with wavelength greater than the ion Larmor radius rL+ (k⊥ rL+ < 1), propagate in a plasma characterized by large ion plasma frequencies (). Using an ordering parameter ε, we separated out two dispersion relations, one of which is independent of the relativistic terms, while the other depends sensitively on them. The solutions of the former dispersion relation yield two modes: a low-frequency (LF) mode with a frequency ω < ω+ and a high-frequency (HF) mode with ω > ω+. The plasma is stable to the propagation of these modes. The latter dispersion relation yields a new LF mode in addition to the modes supported by the non-relativistic dispersion relation. The two LF modes can coalesce to make the plasma unstable. These results are also verified numerically using a standard root solver.

Finite-frequency surface waves on current sheets

1991 ◽  
Vol 45 (3) ◽  
pp. 389-406 ◽  
Author(s):  
K. P. Wessen ◽  
N. F. Cramer
Keyword(s):  
Magnetic Field ◽  
Dispersion Relation ◽  
Surface Waves ◽  
Cyclotron Frequency ◽  
Low Frequency ◽  
Dielectric Tensor ◽  
Magnetic Field Direction ◽  
Field Reversal ◽  
Ion Cyclotron ◽  
The Magnetic Field

The dispersion relation for low-frequency surface waves at a current sheet between two magnetized plasmas is derived using the cold-plasma dielectric tensor with finite ion-cyclotron frequency. The magnetic field direction is allowed to change discontinuously across the sheet, but the plasma density remains constant. The cyclotron frequency causes a splitting of the dispersion relation into a number of mode branches with frequencies both less than and greater than the ion-cyclotron frequency. The existence of these modes depends in particular upon the degree of magnetic field discontinuity and the direction of wave propagation in the sheet relative to the magnetic field directions. Sometimes two modes can exist for the same direction of propagation. The existence of modes undamped by Alfvén resonance absorption is predicted. Analytical solutions are obtained in the low-frequency and magnetic-field-reversal limits. The solutions are obtained numerically in the general case.

Theory of stimulated scattering of large-amplitude waves

1995 ◽  
Vol 53 (2) ◽  
pp. 213-222 ◽  
Author(s):  
L. Stenflo
Keyword(s):  
Dispersion Relation ◽  
Large Amplitude ◽  
Pump Wave ◽  
Low Frequency ◽  
Wave Frequency ◽  
Nonlinear Coupling ◽  
Stimulated Scattering ◽  
Pump Wave Frequency ◽  
General Dispersion ◽  
Electron Gyrofrequency

By means of the standard fluid equations, we consider the nonlinear coupling between a large-amplitude pump wave and the low-frequency modes in a collisional plasma. We derive the general dispersion relation in order to discuss the case where the pump-wave frequency is not much larger than the electron gyrofrequency.

scholarly journals Collisionless Damping of Fast and Ion?Cyclotron Surface Waves

1993 ◽  
Vol 46 (2) ◽  
pp. 271 ◽  
Author(s):  
GW Rowe
Keyword(s):  
Surface Waves ◽  
Short Wavelength ◽  
Mode Conversion ◽  
Low Frequency ◽  
Wave Mode ◽  
Alfven Wave ◽  
Field Boundary ◽  
First Order ◽  
Vacuum Interface ◽  
Ion Cyclotron

A recently developed general kinetic theory of surface waves is used to calculate the collisionless damping of low frequency fast and ion-cyclotron surface waves on a magnetised plasma-vacuum interface. In particular, the possibility of Cherenkov (Landau and transit-time magnetic) absorption by electrons is accounted for, assuming a bi-Maxwellian distribution of electrons in velocity space. It is shown that in general the surface waves are damped via mode conversion to a short-wavelength mode, such as the kinetic Alfven wave, which is subsequently Landau absorbed within the plasma. For high temperatures this short-wavelength mode can also be radiated into the plasma without being completely absorbed. It is also shown that the related ion-sound surface wave mode and instability identified by Alexandrov et al. (1984) are unphysical, and are the result of neglecting the gas pressure in the first-order magnetic field boundary condition.

The effect of neutral-gas friction on Alfvén surface waves propagating along a plasma–vacuum interface

1998 ◽  
Vol 60 (4) ◽  
pp. 731-742 ◽  
Author(s):  
NAGENDRA KUMAR ◽  
KRISHNA M. SRIVASTAVA
Keyword(s):  
Dispersion Relation ◽  
Surface Waves ◽  
Mode Structure ◽  
Astrophysical Plasmas ◽  
Interstellar Clouds ◽  
The Real ◽  
Viscosity Parameter ◽  
Neutral Gas ◽  
Vacuum Interface ◽  
Coefficient Of Viscosity

The effect of neutral-gas friction on Alfvén surface waves propagating along an infinitely conducting viscous plasma–vacuum interface has been investigated. A dispersion relation is obtained for such waves. For different values of the neutral-gas friction parameter S=νc/ω (where νc is the collisional frequency between two components of the composite plasma), the variations of the real and imaginary parts kr and ki of the wavenumber k with the viscosity parameter vp= μlω/ρ01v2A1 (where μl and ρ01 are the coefficient of viscosity and the density of plasma media 1) are shown graphically. It is concluded that a three-mode structure of Alfvén surface waves results flowing to neutral-gas friction. It is suggested that our results are useful for both laboratory and astrophysical plasmas (e.g. photospheres, chromospheres and cool interstellar clouds).

scholarly journals Twisted modes instability of electron–positron shell interacted with moving ion background

2017 ◽  
Vol 35 (3) ◽  
pp. 543-550 ◽  
Author(s):  
D. Nobahar ◽  
K. Hajisharifi ◽  
H. Mehdian
Keyword(s):  
Dispersion Relation ◽  
Laboratory Experiments ◽  
Theory Approach ◽  
Temperature Anisotropy ◽  
Ion Plasma ◽  
Electron Positron ◽  
Electrons And Positrons ◽  
Positron Concentration ◽  
General Dispersion ◽  
Instability Growth

AbstractIn this paper, the instability of electrostatic twisted modes carrying orbital angular momentum in the moving electron–positron–ion plasma is investigated. In the kinetic theory approach, the general dispersion relation of twisted modes is derived by using Laguerre–Gaussian perturbed distribution function and electrostatic potential in the paraxial limit. Utilizing the obtained general dispersion relation for a specific case of electron–positron (e–p) shell with temperature anisotropy interacted with moving ion background, the effects of angular mode number, electrons and positrons temperature, and positron concentration on the group velocity and instability growth rate of twisted waves are illustrated, numerically. The results of the present investigation will greatly attribute to the understanding of e–p jet dynamic in astrophysical environments and laboratory experiments where the twisted modes can play a central role as a perturbed term.

Low-frequency drift-induced instabilities in a magnetized two-ion plasma

1986 ◽  
Vol 35 (3) ◽  
pp. 393-412 ◽  
Author(s):  
R. Bharuthram ◽  
M. A. Hellberg
Keyword(s):  
Dispersion Relation ◽  
Numerical Solutions ◽  
Cyclotron Frequency ◽  
Low Frequency ◽  
Frequency Drift ◽  
Transition Diagram ◽  
Electrostatic Waves ◽  
Ion Plasma ◽  
Parameter Values ◽  
A Current

Numerical solutions of a dispersion relation for low-frequency electrostatic waves in a current-carrying, cold, weakly collisional, magnetized two-ion plasma are used to discuss the two-stream and resistive natures of the ion-ion hybrid instability. An instability with analogous behaviour is found to be associated with the light ion cyclotron frequency. Analytical results explain the behaviour. A numerically derived transition diagram summarizes the parameter values for which transitions between different modes take place.

Local kinetic analysis of low-frequency electrostatic modes in tokamaks

1991 ◽  
Vol 69 (2) ◽  
pp. 102-106
Author(s):  
A. Hirose
Keyword(s):  
Dispersion Relation ◽  
Kinetic Analysis ◽  
Low Frequency ◽  
Acoustic Mode ◽  
Landau Damping ◽  
Trapped Electrons ◽  
Ion Acoustic ◽  
Transit Frequency

Analysis, based on a local kinetic dispersion relation in the tokamak magnetic geometry incorporating the ion transit frequency and trapped electrons, indicates that modes with positive frequencies are predominant. Unstable "drift"-type modes can have frequencies well above the diamagnetic frequency. They have been identified as the destabilized ion acoustic mode suffering little ion Landau damping even when [Formula: see text].

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