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Dec 1986

Volume 29, Issue 12, pp. 3907-4233

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The Lagrangian–Eulerian probability relations and the random force method for nonhomogeneous turbulence

E. A. Novikov

Phys. Fluids 29, 3907 (1986); http://dx.doi.org/10.1063/1.865778 (3 pages) | Cited 7 times

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The relations between Lagrangian and Eulerian probabilities are obtained for the case of variable density of fluid. The general stochastic model for trajectories in nonhomogeneous turbulence is considered, and probability for Lagrangian forcing is expressed in terms of Eulerian distribution. The criterion of the influence of boundaries on the asymptotic behavior of trajectories is presented.
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47.27.T- Turbulent transport processes
47.27.N- Wall-bounded shear flow turbulence
51.10.+y Kinetic and transport theory of gases
92.60.hk Convection, turbulence, and diffusion

Wave propagation on the von Karman trail

Chjan C. Lim and Lawrence Sirovich

Phys. Fluids 29, 3910 (1986); http://dx.doi.org/10.1063/1.865779 (2 pages) | Cited 5 times

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The presence of wave propagation on vortex trails has been pointed out by Tritton [J. Fluid Mech. 6, 547 (1959)] who measured their speeds in the wake of a cylinder at moderate Reynolds numbers. It is shown here that the von Karman model of the vortex trail leads to such disturbance waves and, moreover, that they can be of growing amplitude. The theoretical values of the wave speeds are found to lie within the experimental error bounds.
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47.27.W- Boundary-free shear flow turbulence
47.15.ki Inviscid flows with vorticity
47.35.-i Hydrodynamic waves

Influence of the system response on the coherent structures in a confined shear layer

Denis Veynante, Sebastien M. Candel, and Jean‐Pierre Martin

Phys. Fluids 29, 3912 (1986); http://dx.doi.org/10.1063/1.865780 (3 pages) | Cited 3 times

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The existence of coherent structures in mixing layers is now well‐known but some aspects of their dynamics are not clarified. In particular, the influence of the eigenfrequency of the experimental apparatus on the layer development is generally not studied. The present experimental evidence indicates that the frequency response of an apparently unexcited plane mixing layer is, in fact, a characteristic of the setup.
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47.27.W- Boundary-free shear flow turbulence
47.60.-i Flow phenomena in quasi-one-dimensional systems

A simple composite time scale model for third‐order scalar transports

Myung Kyoon Chung and Nam Ho Kyong

Phys. Fluids 29, 3914 (1986); http://dx.doi.org/10.1063/1.865781 (3 pages) | Cited 1 time

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A simple composite time scale model for third‐order scalar‐velocity correlations under negligible effect of buoyancy is proposed as τ3∝τu(1+bτθ/τu), where τu is a dynamic time scale (≡math2/ϵ) and τθ is a scalar time scale (≡θ2/ϵθ). The constant b represents relative influence of τθ over τu on the spatial transport of second‐order moments. Its value depends on the power of the scalar fluctuations θ in the third‐order moments. The model predictions are in excellent agreement with experimental data in a turbulent scalar diffusion field behind a line heat source in a uniform shear flow.
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47.27.T- Turbulent transport processes
47.27.N- Wall-bounded shear flow turbulence

Transverse oscillations of an electron beam propagating in the ion focused regime

R. F. Schneider and J. R. Smith

Phys. Fluids 29, 3917 (1986); http://dx.doi.org/10.1063/1.865782 (3 pages) | Cited 13 times

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A magnetic probe array is utilized to perform current centroid measurements of a 4 kA, 700 kV, 100 nsec electron beam propagating in the ion focused regime. Results with several filling gases all show transverse oscillation, which may be indicative of hose‐type motions of the beam.
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41.75.Fr Electron and positron beams
52.40.Mj Particle beam interactions in plasmas
52.70.Ds Electric and magnetic measurements

Stokes drag on hollow cylinders and conglomerates

I. A. Lasso and P. D. Weidman

Phys. Fluids 29, 3921 (1986); http://dx.doi.org/10.1063/1.865732 (14 pages) | Cited 28 times

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An experimental study of the drag on hollow cylinders and conglomerates falling in a viscous fluid under Stokes flow conditions is described. The experiments were carried out in a tank of square cross section using silicone oil as the Newtonian fluid. Settling velocities of the free falling objects were measured and corrected to conditions of zero Reynolds number flow in an unbounded fluid. The results reveal that all objects tested have Stokes settling velocities smaller than that of a sphere of equal mass and volume. Measurements are reported in terms of the settling speed ratio defined as the ratio of the Stokes settling speed to that of a sphere of equal mass and volume. For the hollow cylinders two parameters are varied: the aspect ratio (length to outside diameter) and the radius ratio (inner to outer radius). Measurements show that the settling speed ratio decreases markedly as the hollowness of the cylinder increases. Each fixed radius ratio data set exhibits a maximum settling speed ratio near an aspect ratio of 1.65. For conglomerates composed of n spheres two trends appear: one for planar configurations and the other for globular clusters. Experimental data for two spheres and three spheres in point contact are in good agreement with recent theoretical results.
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51.20.+d Viscosity, diffusion, and thermal conductivity
47.15.G- Low-Reynolds-number (creeping) flows

The effects of inertia on the buoyancy‐driven convection flow in settling vessels having inclined walls

E. S. G. Shaqfeh and A. Acrivos

Phys. Fluids 29, 3935 (1986); http://dx.doi.org/10.1063/1.865733 (14 pages) | Cited 9 times

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The bulk‐averaged equations of motion, which describe the buoyancy driven flow in particle settlers having inclined walls, are solved over a wide range of the relevant parameter space. The solution assumes that the flow is laminar, that the particle Reynolds number is small, that the suspension is monodisperse, and that the settling occurs in a parallel plate vessel whose length to width ratio is not too large. It is shown that, in the asymptotic limit, Λ→∞, where Λ is the ratio of a sedimentation Grashof number to a sedimentation Reynolds number, R, inertial effects in the flow are O(ξ1/6), where ξ is given explicitly in terms of R, Λ, the inclination angle, θ, and the dimensionless distance from the vessel bottom. Using regular and singular perturbation techniques, the asymptotic form of the equations for Λ≫1 are then solved over the entire range of ξ and the solutions are shown to reduce to those given by Acrivos and Herbolzheimer [J. Fluid Mech. 92, 435 (1979)] and by Schneider [J. Fluid Mech. 120, 323 (1982)] in the limits ξ→0 and ξ→∞, respectively. Since typically in practice Λ∼O(106–109), the present solutions give expressions for the velocity profiles and the thickness of the clear‐fluid slit that forms underneath the downward facing vessel wall, which are valid for a wide class of systems of practical interest.
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47.15.-x Laminar flows
47.32.Ef Rotating and swirling flows
47.55.Kf Particle-laden flows

Buoyancy‐driven convection in a horizontal fluid layer extending over a porous substrate

D. Poulikakos

Phys. Fluids 29, 3949 (1986); http://dx.doi.org/10.1063/1.865734 (9 pages) | Cited 17 times

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In this study a series of numerical simulations is reported that aims to document the phenomenon of buoyancy‐driven flow instability in a fluid layer extending over a porous substrate. The numerical simulations focus primarily on the parametric domain in which the flow in the system is well established, i.e., the value of the Rayleigh number is larger than critical. A general flow model is used to describe the flow inside the porous bed. This flow model accounts for friction caused by macroscopic shear [Brinkman extension of the Darcy model; Appl. Sci. Res. Sect. A 1, 27 (1947)], as well as for the phenomenon of flow inertia [Forchheimer’s extension of the Darcy model; Dtsch. Ingenieure 45, 1782 (1901)]. Several important characteristics of the flow and temperature fields inside the composite layer (porous/fluid) are reported and the dependence of these characteristics on the problem dimensionless groups is documented.
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47.20.Bp Buoyancy-driven instabilities (e.g., Rayleigh-Benard)
47.56.+r Flows through porous media
47.27.T- Turbulent transport processes
47.15.-x Laminar flows

Pouring flows

Jean‐Marc Vanden‐Broeck and Joseph B. Keller

Phys. Fluids 29, 3958 (1986); http://dx.doi.org/10.1063/1.865735 (4 pages) | Cited 23 times

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Free surface flows of a liquid poured from a container are calculated numerically for various configurations of the lip. The flow is assumed to be steady, two dimensional, and irrotational; the liquid is treated as inviscid and incompressible; and gravity is taken into account. It is shown that there are jetlike flows with two free surfaces, and other flows with one free surface which follow along the underside of the lip or spout. The latter flows occur in the well‐known ‘‘teapot effect,’’ which was treated previously without including gravity. Some of the results are applicable also to flows over weirs and spillways.
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68.03.Kn Dynamics (capillary waves)
68.05.-n Liquid-liquid interfaces
47.15.Cb Laminar boundary layers
47.10.-g General theory in fluid dynamics

Steady flow past a sluice gate

P. M. Naghdi and L. Vongsarnpigoon

Phys. Fluids 29, 3962 (1986); http://dx.doi.org/10.1063/1.865736 (9 pages) | Cited 1 time

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The problem of steady two‐dimensional flow, under the action of gravity, of an incompressible inviscid fluid sheet past a sluice gate is reexamined with particular reference to the theoretical prediction of the contraction ratio, i.e., the ratio of the far downstream height to the sluice opening. The problem is formulated here by a direct approach with the use of the theory of a directed fluid sheet, which includes appropriate jump conditions arising in a natural way within the scope of the basic theory. The determination of the contraction ratio is effected by a novel procedure in the utilization of the jump conditions at the gate. Detailed numerical calculations are made for two different sluice openings and these provide very good agreement with the experimental results of Benjamin [J. Fluid Mech. 1, 227 (1956)].
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47.15.-x Laminar flows

Experiments on nonlinear cross waves

S. Lichter and L. Shemer

Phys. Fluids 29, 3971 (1986); http://dx.doi.org/10.1063/1.865737 (5 pages) | Cited 9 times

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Surface water waves are generated by a paddle‐type wavemaker operating at one end of a long tank. In addition to a progressing wave field at the forcing frequency, a subharmonic cross wave is generated in the neighborhood of the wavemaker. At lower forcing amplitudes there is a Benjamin–Feir instability of the progressing wave. At large forcing amplitudes, the fundamental decays rapidly along the channel. The cross wave dominates the near field and is strongly modulated on a slow time scale. During each modulation period a soliton propagates away from the wavemaker. The near‐field standing cross wave undergoes a transformation into a progressing wave in the far field.
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47.35.-i Hydrodynamic waves
47.20.Ky Nonlinearity, bifurcation, and symmetry breaking

Evolution of a non‐self‐preserving thermal mixing layer

J. L. Lumley

Phys. Fluids 29, 3976 (1986); http://dx.doi.org/10.1063/1.865738 (6 pages) | Cited 8 times

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In an attempt to explain apparently anomalous measurements, a first integral of the equation relating mean temperature and heat flux is obtained using a Gram–Charlier representation. This permits relating moments of the heat flux distribution to derivatives of coefficients in the mean temperature representation. The same sort of analysis is applied to the temperature variance equation, giving other relations among coefficients. It is concluded that the measurements are consistent with a very small and rapidly decaying fourth‐order component which has a surprisingly large effect on the maximum value of the heat flux. It is found that the evolution of the layer certainly cannot be described by an eddy viscosity. Several relations (e.g., connecting the integral of the heat flux with the growth of the length scale, and another giving an estimate for the temperature variance) are thought to be new, are not limited by assumptions of self‐preservation, and should prove useful in analyzing other data.
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47.27.W- Boundary-free shear flow turbulence
47.27.T- Turbulent transport processes
47.27.Gs Isotropic turbulence; homogeneous turbulence

Wave structures in jets of arbitrary shape. I. Linear inviscid spatial instability analysis

Shozo Koshigoe and Arnold Tubis

Phys. Fluids 29, 3982 (1986); http://dx.doi.org/10.1063/1.865739 (11 pages) | Cited 13 times

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Green function methods are used to give a practical form of the Rayleigh linear inviscid instability analysis for jets of arbitrary mean flow profile. Simple illustrations of the general methodology are given for vortex‐sheet and continuous‐velocity‐profile shear layers. Some of the numerical results for elliptic jets are compared with those previously obtained from solutions of Mathieu’s equation in elliptic cylindrical coordinates.
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47.20.Ft Instability of shear flows (e.g., Kelvin-Helmholtz)
47.60.Kz Flows and jets through nozzles
47.40.Ki Supersonic and hypersonic flows
47.32.Ef Rotating and swirling flows

Numerical simulation of a laminar end‐wall vortex and boundary layer

Tim Wilson and Richard Rotunno

Phys. Fluids 29, 3993 (1986); http://dx.doi.org/10.1063/1.865740 (13 pages) | Cited 9 times

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The fluid dynamics of a laminar axisymmetric end‐wall vortex is investigated through high‐resolution numerical integrations of the Navier–Stokes equations. The predicted velocity field is shown to be in good to excellent agreement with a concurrent laboratory investigation. The dynamics of the boundary layer and core regions are found to be mostly inviscid. Thin viscous sublayers in the boundary layer and core vanish in the vicinity of the inviscid corner region. The effectively inviscid nature of most of the flow is demonstrated by examining the balance of terms in the momentum equations and by the applicability of the inviscid swirl equation rη=r2(dH/dΨ)−(d/dΨ)(Γ2/2) to most of the flow.
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47.15.ki Inviscid flows with vorticity
47.15.Cb Laminar boundary layers
02.60.Jh Numerical differentiation and integration

Axisymmetric problem of vortex sound with solid surfaces

T. Miyazaki and T. Kambe

Phys. Fluids 29, 4006 (1986); http://dx.doi.org/10.1063/1.865741 (10 pages) | Cited 8 times

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A general formulation of the axisymmetric vortex sound is given, and three typical problems are considered in detail, in which the acoustic wave is generated by a vortex ring interacting with either a sphere, a circular disk, or a circular aperture of a plane wall in an axisymmetric manner. The velocity potentials induced by the vortex in the presence of the body are determined by the method of dual integral equations or the image vortex. From the vortex trajectories, the acoustic wave fields are determined. The method of matched asymptotic expansions yields the result that the force exerted on the body is related to the profile of the dipole component. It is also found that the wave amplitude is expressed in terms of the value of a streamfunction at the vortex position, which represents a hypothetical potential flow around the body and is defined appropriately in each problem.
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47.27.Sd Turbulence generated noise
47.40.Dc General subsonic flows
43.28.+h Aeroacoustics and atmospheric sound
47.10.-g General theory in fluid dynamics

Isotropic forms of vorticity and velocity structure function equations in several turbulent shear flows

D. A. Shah and R. A. Antonia

Phys. Fluids 29, 4016 (1986); http://dx.doi.org/10.1063/1.865742 (9 pages) | Cited 4 times

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Isotropic forms of the vorticity and velocity structure function equations are valid in the logarithmic regions of a fully developed turbulent duct flow and a boundary layer over a wide range of Reynolds numbers. These equations are also valid in a low Reynolds number turbulent wake and a high Reynolds number atmospheric surface layer. However, these equations are not satisfied in the near‐wall region of duct and boundary layer flows where the production of vorticity is significantly larger than the dissipation. The appropriateness of the equations as indicators of local isotropy is discussed in the context of the present and other published measurements.
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47.27.Gs Isotropic turbulence; homogeneous turbulence
47.27.N- Wall-bounded shear flow turbulence
47.27.T- Turbulent transport processes

Navier–Stokes boundary conditions of a gas mixture

G. Lohöfer

Phys. Fluids 29, 4025 (1986); http://dx.doi.org/10.1063/1.865743 (7 pages) | Cited 1 time

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The Navier–Stokes velocity and density boundary conditions of a multicomponent gas mixture in front of a wall are considered. The following gas–wall interactions are taken into account: partially inelastic interactions between the gas molecules and the wall (accommodation), conversion among the different molecule species (ionization, etc.), and gas flow through the wall. Since the influence of the kinetic boundary layer on the gas continuum is negligible, the moments in the boundary conditions for the Navier–Stokes equations are calculated with the first‐order Chapman–Enskog solution (Maxwell’s method).
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47.60.-i Flow phenomena in quasi-one-dimensional systems
51.10.+y Kinetic and transport theory of gases
68.43.-h Chemisorption/physisorption: adsorbates on surfaces
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces

Overstability in magnetohydrodynamic convection revisited

Krishna Kumar, Jayanta K. Bhattacharjee, and Kalyan Banerjee

Phys. Fluids 29, 4032 (1986); http://dx.doi.org/10.1063/1.865744 (3 pages)

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The question of overstability in the magnetohydrodynamic convection is reexamined in view of the recent exact result stating that the principle of exchange of stabilities is valid only if Qp2≤π2, where Q is the Chandrasekhar number and p2 is the magnetic Prandtl number. It is shown by writing explicit solutions that in the limit Q≫1 and p2≪1, overstable oscillations are indeed possible, contradicting the Chandrasekhar–Gibson criterion [Hydrodynamic and Hydromagnetic Stability (Oxford, London, 1961), Chaps. 1 and 4; Proc. Cambridge Philos. Soc. 62, 287 (1966)]. Furthermore, the Chandrasekhar–Gibson criterion is shown to be a necessary condition for a codimension‐2 bifurcation, but this is not a necessity for overstability.
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47.65.-d Magnetohydrodynamics and electrohydrodynamics
47.27.T- Turbulent transport processes
47.20.Ky Nonlinearity, bifurcation, and symmetry breaking

Evolution of electron hole and electron wave pulses in a single‐ended magnetoplasma

S. Iizuka and H. Tanaca

Phys. Fluids 29, 4035 (1986); http://dx.doi.org/10.1063/1.865745 (5 pages)

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Formation and propagation of the electron phase‐space hole and electron wave pulse (Trivelpiece–Gould mode) are experimentally investigated in a single‐ended plasma in the very first stage of double layer formation. As soon as the rarefaction pulse excited at a collector terminating the plasma arrives at a plasma source, the electron holes are formed and propagate toward the collector with a speed comparable to the electron thermal speed. The electron energy distribution function dips at the hole and becomes broader in the upper stream region of hole propagation. The compression pulse formed in front of the plasma source just after rarefaction pulse arrival does not have a direct effect on the hole excitation.
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52.35.Mw Nonlinear phenomena: waves, wave propagation, and other interactions (including parametric effects, mode coupling, ponderomotive effects, etc.)
52.35.Fp Electrostatic waves and oscillations (e.g., ion-acoustic waves)

The single‐particle and collective descriptions of the anomalous Doppler resonance and the role of ion dynamics

R. O. Dendy, C. N. Lashmore‐Davies, and A. Montes

Phys. Fluids 29, 4040 (1986); http://dx.doi.org/10.1063/1.865746 (7 pages) | Cited 3 times

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The connection between three aspects—single‐particle, beam, and continuous velocity distribution—of the anomalous Doppler effect are investigated. The key quantity is the power Re(j ⋅ E∗) dissipated by electrostatic waves interacting with a non‐Maxwellian electron velocity distribution. Its spatial components describe energy flows that are the counterparts in classical electrodynamics to the quantum properties of the single‐particle anomalous Doppler effect. A complete plasma physics treatment requires the inclusion of ion dynamics. Examination of the large‐k region of wavenumber space—in contrast to the well‐known small‐k region—shows that ion Landau damping is important in stabilizing plasmas for which the electron velocity distribution considered alone is destabilizing. Finally, by choosing simple models for the superthermal electron velocity distribution, general features of the instability, and those specific to particular tail models, are identified analytically and numerically.
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52.35.Fp Electrostatic waves and oscillations (e.g., ion-acoustic waves)
52.35.Qz Microinstabilities (ion-acoustic, two-stream, loss-cone, beam-plasma, drift, ion- or electron-cyclotron, etc.)
94.30.cq MHD waves, plasma waves, and instabilities

Linear stability analysis of the Vlasov–Poisson equations in high density plasmas in the presence of crossed fields and density gradients

D. J. Kaup, P. J. Hansen, S. Roy Choudhury, and Gary E. Thomas

Phys. Fluids 29, 4047 (1986); http://dx.doi.org/10.1063/1.865747 (8 pages) | Cited 7 times

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A method is presented for the linear stability analysis of the Vlasov–Poisson equations in high density, finite temperature plasmas in the presence of inhomogeneous crossed fields and density gradients. The method is more general than earlier studies of high‐β inhomogeneous plasmas in that various approximations employed therein such as the local approximation (JWKB), low‐frequency, or small wavelength restrictions are not employed here. Although only the nonrelativistic electrostatic planar case is treated, the method, with due modification, could be extended into the relativistic electromagnetic regime. The method uses a singular perturbation expansion to construct the unperturbed single particle orbits. Then with these orbits the ‘‘integration over the unperturbed orbits’’ necessary for determining the perturbed distribution function is performed. The initial distribution function may be quite general, but the expansions used do assume a distribution close to that of a sheared laminar flow. The perturbed distribution function is obtained as a singular perturbation expansion also. Lastly, the application of the method is demonstrated by reducing the linearized Vlasov–Poisson equations, with inhomogeneous electric fields and density gradients, to a second‐order ordinary differential equation where the frequency is an eigenvalue. Similarities to and differences from the cold‐fluid equations are pointed out.
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52.27.Jt Nonneutral plasmas
52.20.Dq Particle orbits
52.25.Dg Plasma kinetic equations

Stimulated Brillouin scattering of whistler waves off the kinetic Alfvén waves in plasmas

R. P. Sharma, W. Rozmus, and A. A. Offenberger

Phys. Fluids 29, 4055 (1986); http://dx.doi.org/10.1063/1.865748 (5 pages) | Cited 6 times

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In this paper an investigation of the parametric process is presented in which a high‐power whistler wave decays into another whistler wave and a low‐frequency kinetic Alfvén wave (mixed mode), viz., the stimulated Brillouin scattering of a whistler. The dominant coupling in the equation for the scattered whistler arises from the electron motion along the static magnetic field in the low‐frequency wave and the partially electrostatic nature of the kinetic Alfvén wave. On the other hand, interaction of two whistler waves leads to a component of the ponderomotive force along the static magnetic field. This component is responsible for the electrostatic part of the kinetic Alfvén wave. Explicit expressions for the growth rate and threshold power are given. At a pump power of ∼1 kW, the growth time of this parametric process comes out to be ∼5 μsec for the parameters of the mirror device. For the magnetospheric parameters, the convective threshold electric field is ∼0.3 mV/m.
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52.35.Mw Nonlinear phenomena: waves, wave propagation, and other interactions (including parametric effects, mode coupling, ponderomotive effects, etc.)
52.35.Hr Electromagnetic waves (e.g., electron-cyclotron, Whistler, Bernstein, upper hybrid, lower hybrid)
52.50.Gj Plasma heating by particle beams

High‐energy components and collective modes in thermonuclear plasmas

B. Coppi, S. Cowley, R. Kulsrud, P. Detragiache, and F. Pegoraro

Phys. Fluids 29, 4060 (1986); http://dx.doi.org/10.1063/1.865749 (13 pages) | Cited 43 times

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The theory of a class of collective modes of a thermonuclear magnetically confined plasma, with frequencies in the range of the ion‐cyclotron frequency and of its harmonics, is presented. These modes can be excited by their resonant cyclotron interaction with a plasma component of relatively high‐energy particles characterized by a strongly anisotropic distribution in velocity space. Normal modes that are spatially localized by the inhomogeneity of the plasma density are found. This ensures that the energy gained by their resonant interaction is not convected away. The mode spatial localization can be significantly altered by the magnetic field inhomogeneity for a given class of plasma density profiles. Special attention is devoted to the case of a spin polarized plasma, where the charged products of fusion reactions are anisotropically distributed. It is shown that for the mode of polarization that enhances nuclear reaction rates the tritium will be rapidly depolarized for toroidal configurations with relatively mild gradients of the confining magnetic field.
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52.35.-g Waves, oscillations, and instabilities in plasmas and intense beams
52.55.Pi Fusion products effects (e.g., alpha-particles, etc.), fast particle effects

Reduction of order in the geometric optics of plasmas

L. Friedland and G. Goldner

Phys. Fluids 29, 4073 (1986); http://dx.doi.org/10.1063/1.865750 (12 pages) | Cited 9 times

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Small amplitude waves in plasmas are usually described by large systems of linearized Maxwell and kinetic equations. A procedure of elimination of components and reduction of the order of the system is discussed within the geometric optics approximation. In some cases characterized by Hermitian generalized dielectric tensors E describing the unreduced problem, the successive reduction procedure yields, at each step, energy conserving reduced systems that preserve the general form and first‐order nature of the equations. The number of equations in the final reduced system is equal to the number of degenerate vanishing eigenvalues of E. The theory is applied in the case of transverse waves, propagating along the magnetic field in plasmas with plane parallel stratification. Both cold streaming plasma and kinetic problems are considered by using the same‐order reduction procedure. The cold plasma case, at low densities, becomes doubly degenerate at cyclotron resonance, reflecting mode coupling between the vacuum electromagnetic and electron cyclotron modes. Mode conversion coefficients found from the solution of the reduced system of two first‐order differential equations, characterizing this case, are in an excellent agreement with the results of the numerical solutions of the full unreduced system of equations. The kinetic case is approached by viewing the plasma as consisting of many beamlets each governed by the cold fluid approximation. The problem represents a multiply degenerate situation as many beamlets are in resonance at a time. Renormalized perturbation analysis of the partially reduced system in the low‐density case predicts results similar to those found in the cold plasma, with possible broadening of the resonance region. At large densities, for propagation from the lower magnetic field side, the wave is reflected and the cyclotron resonance is inaccessible. In contrast, for propagation from the high magnetic field side, the electromagnetic energy is transferred to the electrons via the mechanism of Landau cyclotron damping.
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52.40.Db Electromagnetic (nonlaser) radiation interactions with plasma
52.50.Gj Plasma heating by particle beams

Electrostatic beam instabilities in a positive/negative ion plasma

Miguel Galvez and S. Peter Gary

Phys. Fluids 29, 4085 (1986); http://dx.doi.org/10.1063/1.865751 (6 pages) | Cited 7 times

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This paper examines the linear theory of electrostatic waves and instabilities in an unmagnetized, homogeneous Vlasov plasma. The first configuration considered is that of a stable plasma with three Maxwellian components: electrons, positive ions, and negative ions. The dispersion properties of the lightly damped ion modes are studied as a function of relative electron density and relative component temperatures. The second configuration considered is that of a tenuous electron–ion beam with drift speed v0b streaming through a negative/positive ion plasma. If the beam is very tenuous, an electron beam instability satisfying ωr≂kv0b is excited; if the beam is more dense, the instability becomes Buneman‐like with parabolic dispersion. The thresholds and maximum growth rates of these instabilities are described as functions of the beam density and drift speed.
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52.35.Fp Electrostatic waves and oscillations (e.g., ion-acoustic waves)
52.35.Qz Microinstabilities (ion-acoustic, two-stream, loss-cone, beam-plasma, drift, ion- or electron-cyclotron, etc.)
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