... is sufficiently above a damping-determined threshold but below a threshold for temporal or absolute instability exists for the backscatter instabilities. ...
DTIC Science & Technology
The threshold for an absolute parametric instability of the decay type along with the growth rates for two types of interacting oscillations are obtained theoretically for an inhomogeneous plasma layer. (AIP)
Energy Citations Database
For one-dimensional three-wave parametric instabilities with oppositely directed group velocities for the decay waves in unbounded plasmas, it is known that for uniform coupling amplitude and constant wave-vector mismatch (dsummationk/sub i//dx = const) there cannot be an absolute instability. It is shown that this ...
... The ratio of absolute and convective instability thresholds is large whenever the damping lengths of the linear uncoupled modes have very ...
... to the influence of a powerful pumping wave is unstable relative to the build up of plasma high-frequency electronic waves (plasmons); this is ...
The nonlinear stage of the absolute parametric instability in an inhomogeneous bounded plasma is examined theoretically.(AIP)
We investigate the effect of coupling between diffraction and walk-off on secondary instabilities in nondegenerate optical parametric oscillators. We show that traveling waves that propagate in the walk-off direction, which are generated at the onset of absolute instability, experience Eckhaus and zigzag phase ...
PubMed
A theory is derived for the absolute parametric instabilities which are excited in a nonuniform magnetized plasma by electromagnetic radiation at a frequency comparable to the electron plasma frequency. The thresholds and growth rates are determined for the aperiodic instability, for the decay into a lower-hybrid ...
The possibility of deep parametric decay instability suppression by launching a complementary (small power) pump wave possessing a slightly shifted frequency is demonstrated experimentally. This suppression is achieved at an additional pump wave frequency shift equal to the frequency separation of ion acoustic eigenmodes excited in plasma as a result of ...
NASA Astrophysics Data System (ADS)
The parametric decay of an electromagnetic wave into two electron plasma waves is considered. The electromagnetic wave is obliquely incident on the density gradient. The resulting analysis shows that the threshold for absolute instability decreases as the...
National Technical Information Service (NTIS)
An integral equation is derived to describe the absolute instability in an inhomogeneous plasma.(AIP)
Previous absolute instability results for significant growth from a parametric instability involving oppositely directed modes coupled by a uniform pump with phase inflection coupling (..delta..k = k''x/sup 2//2) are extended to higher modes and to thresholds. The results are applied to stimulated ...
A theory is developed of absolute parametric aperiodic instability in a spatially inhomogeneous plasma, when the electromagnetic waves generated in the plasma are trapped by the plasma near the peaks of the pumping-wave field.
Finite-bandwidth effects are investigated by using the random phase approximation. The conditions of validity are checked by solving exactly a particular model. It is found that a finite coherence length for the pump wave can favor the existence of absolute instability. (AIP)
A spatially localized instability t..-->..l+s, whose properties are in agreement with the predictions of the linear and nonlinear theories, was detected in the inhomogeneous plasma in the region of the field peak in front of the reflection point of the pump wave.
Parametric instability l ..-->.. l'+s resulting in anomalous reflection of oblique Langmuir waves in a two-dimensionally nonuniform plasma is studied experimentally and theoretically. The experimental results confirm the theoretical prediction that for low input powers, the instability consists in the spatial amplification ...
A plasma subjected to the action of an intense pumping verve is unstable with respect to buildup of plasma high-frequency electron waves (plasmons) due to decay of the pumping wave into two plasmons. The effect of spatial inhomogeneity of the plasma on such parametric instability is studied. It is shown that allowance for spatial inhomogeneity of ...
It is shown that an absolute instability arising from the spatial variation of the pump wave can occur in an inhomogeneous plasma. An analysis is carried out for the example of the parametric conversion of a pump wave into a plasma wave and an ion-acoustic wave. In this instability, the perturbations whose ...
Using WKB analysis it is shown that for three-wave backscattering type parametric instabilities in inhomogeneous plasmas no spatial (convective) growth is possible for undamped modes. if one coupled mode is more heavily damped than the other, then spatial growth is possible in both forward and back-scattering. The spatial amplification factor is ...
The parametric decay of an electromagnetic wave into two electron plasma waves is considered. The electromagnetic wave is obliquely incident on the density gradient. The resulting analysis shows that the threshold for absolute instability decreases as the angle of incidence of the electromagnetic wave relative to the density gradient ...
The parametric decay of an electromagnetic wave into two electron plasma waves in an inhomogeneous plasma is considered. The electromagnetic wave is obliquely incident on the density gradient. The resulting analysis shows that the threshold for absolute instability decreases as the angle of incidence of the electromagnetic wave ...
The effect of spatial background turbulence on parametric interactions in an infinite, inhomogeneous plasma with a linear density profile is considered. It is shown that the well-known convective saturation arising from the density gradient can disappear in the presence of turbulence. Absolute instability then occurs. The ...
Parametric instabilities in the presence of sinusoidal plasma density modulation are considered analytically and by numerical integration of the coupled mode equations. The density modulation tends to reduce temporal and spatial growth rates. If there is a linear density gradient in addition to the density modulation, the usual convective saturation exists ...
... Descriptors : *CHARGED PARTICLES, *COHERENT RADIATION, *RESONANCE, *CYCLOTRONS, *PARAMETRIC INSTABILITY, SYMPOSIA ...
The paper presents an analysis of the parametric excitation of surface waves propagating in Voigt geometry at the semiconductor-metal boundaries in a semiconductor layer bounded by metal surfaces. It is shown that, in a uniform HF pump field, two waves are excited which are localized at the layer boundaries and propagate in opposite directions at the same phase velocities. ...
A theoretical study of parametric absorption in electron cyclotron resonance heating (ECRH) of tokamak plasmas is presented. The problem of primary and secondary decays including their temporal and spatial growth rates is studied. In the nonlinear phase of development of the excited waves, a cascading saturation mechanism is invoked for both convective and ...
A plasma which is subjected to the influence of a powerful pumping wave is unstable relative to the build up of plasma high-frequency electronic waves (plasmons); this is caused by the decay of the pumping wave into two plasmons. The article that follows ...
The linearized coupled-mode equations in two dimensions are solved numerically within the paraxial approximation to find the absolute-mode threshold of parametric instabilities driven by an incoherent laser beam. The results show that, for plasma lengths only a few times threshold, a surprisingly small temporal bandwidth {Delta}{omega} ...
Convective and absolute nature of instabilities in nondegenerate optical parametric oscillators with large transverse section, for negative detunings and in the presence of walkoff, is examined. The asymptotic response of the signal and idler fields to a transverse localized two-dimensional perturbation is evaluated. The presence of ...
Electrostatic lower hybrid ''pump'' waves are often launched into tokamak plasmas by structures (e.g., waveguides) whose dimensions are considerably smaller than characteristic plasma sizes. Such waves propagate in well-defined resonance cones and give rise to parametric instabilities driven by electron E x B velocities. ...
A general approximate criterion is developed (via WKB analysis) for the absolute instability of two parametrically pumped decay waves with one-dimensional inhomogeneity. The absolute instability threshold pump power proves to be higher than that required for amplitude amplification R by a ...
Electrostatic lower hybrid ''pump'' waves often launched into tokamak plasmas by structures (e.g., waveguides) whose dimensions are considerably smaller than characteristic plasma sizes. Such waves propagate in well-defined resonance cones and give rise to parametric instabilities driven by electron E x B velocities. The ...
Harmonic generation and parametric decay are examined in a toroidal ACT-1 plasma using electrostatic plate antennas. The harmonic generation, which is consistent with sheath rectification, is sufficiently strong that the nonlinearly generated harmonic modes themselves decay parametrically. Resonant and nonresonant parametric decay of ...
Harmonic generation and parametric decay are examined in a toroidal ACT-I plasma using electrostatic plate antennas. The harmonic generation, which is consistent with sheath rectification, is sufficiently strong that the nonlinearly generated harmonic modes themselves decay parametrically. Resonant and nonresonant parametric decay of ...
DOE Information Bridge
The plan of the paper is as follows. Section 1 reviews and extends the linear theory of parametric instabilities in uniform plasma including the effects of a magnetic field. Section 2 calculates the nonlinear saturation of the parametric instability in a ...
The parametric instability of an inhomogeneous pump field with respect to the excitation of high-frequency and low-frequency perturbations is analyzed. Near an intensity maximum of the inhomogeneous field, an absolute modulation instability can occur. The instability threshold, the growth ...
The effects of the inhomogeneities of the number density and the magnitude of the magnetostatic field on the characteristics of the parametrically excited instability of the extraordinary mode near the upper-hybrid resonant frequency are investigated for the case in which the pump wave and the backscattered idler wave are both ordinary modes. The three ...
The space and time behavior of the decay waves is computed analytically in the regime of standard parametric decay. The plasma is assumed to be homogeneous and bounded. The pump wave has a finite pulse duration. The propagation of the pump wave is taken into account, its depletion is ignored. The parametric growth is solved in terms of fluctuating initial ...
... Accession Number : ADA087742. Title : Parametric Instabilities of Electron Cyclotron Waves in Plasmas. Descriptive Note : Technical rept.,. ...
The space and time behavior of parametric backscattering instabilities is computed analytically in the so-called modified decay regime. The plasma is assumed to be homogeneous and of finite length. The propagation of the pump wave and its finite pulse duration both are taken into account, its depletion is ignored. The parametric growth ...
An externally applied large amplitude circularly polarized ion cyclotron wave of long wavelength propagating along the static magnetic field can drive instabilities of ion cyclotron waves and ion acoustic waves. The dispersion relation is first derived using a kinetic equation approach. Later, it is shown that the same relation can be derived on the basis of a ...
The contents of this book are: Plasma as a Dielectric Medium; Nyquist Technique; Absolute and Convective Instabilities; Landau Damping and Phase Mixing; Particle Trapping and Breakdown of Linear Theory; Solution of Viasov Equation via Guilding-Center Transformation; Kinetic Theory of Magnetohydrodynamic Waves; Geometric Optics; Wave-Kinetic Equation; ...
... Descriptors : *DRAG, *BETATRONS, *PARAMETRIC INSTABILITY, MAGNETIC FIELDS, MODIFICATION, VACUUM CHAMBERS, ELECTRON ...
... NO- %42 Plasma 'Heating Through Parametrically Induced Turbulence ... Plasma Plasma instabilities Parametric instabilities Plasma heating ...
Two aspects of the stability of a compressible mixing layer: Absolute/Convective instability and the
NASA Technical Reports Server (NTRS)
An absolute parametric instability which occurs in an inhomogeneous plasma with long-wave turbulence is analyzed in detail. The average characteristics of the instability (the growth rates and the average number of unstable modes) and also the distribution functions of these characteristics are derived for a static ...
The effect of viscosity on the capillary instability of a liquid jet is examined. The critical Weber
Absolute/Convective Instabilities. The concept of absolute and convective insta- ... absolute instability occurs when the zero lies on the real o axis. ...
NASA Website
The theory of absolute and convective instabilities in a plasma is discussed, and it is questionable, as it describes the linear development of instabilities by their behavior in the time asymptotic limit. In order to make sensible predictions on the line...
The theory of absolute and convective instabilities is discussed and we argue that the basis of the theory is questionable, since it describes the linear development of instabilities by their behaviour in the time asymptotic limit. In order to make sensib...
specifically strong magnetoelastic nonlinearity of this crystal type /see 3/.The pointed out experiments dealt with shear magnetoelastic traveling waves.The WPC of longitudinal sound in magnet as well as shear one of ultrasonic magnetoelastic waves absolute parametrical instability.The intensities of amplified waves
E-print Network
The threshold and initial evolution for the decay of a lower-hybrid wave to two lower-hybrid waves are determined. Included are the effects of convective losses in a three-dimensional lower-hybrid resonance cone geometry and the effects of inhomogeneity appropriate to lower-hybrid heating in a tokamak. It is found that the decay to two lower-hybrid waves differs from other such ...
This paper derives a linear kinetic theory of parametric instabilities in a infinite, homogeneous, fully ionized plasma, with no magnetic field. Important problems of the parametric instabilities are studied, in three dimensions, pumped by a monochromatic...
... propagating at an oblique angle with ... Thus, the magnetic field has a ... COUPLING(INTERACTION), MAGNETIC FIELDS, STABILITY, PARAMETRIC ...
... Accession Number : ADD510168. Title : THE SATURATION SPECTRUM OF PARAMETRIC INSTABILITIES, IN: AGARD CP-138,PAPER NO11. ...
... Title : Parametric Excitation and Suppression of Convective Plasma Instabilities in the High Latitude F-Region Ionosphere. ...
... Title : PARAMETRIC STUDY OF ROCKET MOTOR COMBUSTION INSTABILITY. ... program was conducted with a small-scale rocket engine thrust ...
... EXPERIMENTS ON PARAMETRIC INSTABILITIES AND PLASMA HEATING IN A MAGNETIC FIELD, IN: AGARD CP-138, PAPER NO8. ...
... SURVEY TO SESSION ON PARAMETRIC INSTABILITIES, LABORATOR YEXPERIMENTS AND THEORY, IN: AGARD CP-138, PAPER NO7. ...
... constants, the parametric instability is expected to affect the extraction ... Cambridge, A 02139 University of California I Cyclotron Road Dr. L. Thode ...
... capabilities across the military departments and agencies for Research ... Title : Synchrotron-Betatron Parametric Instability in Free-Electron Lasers. ...
... Abstract : The parametric instability growth rate of ion acoustic and Langmuir waves, driven unstable by two uniform pumps near the Bohm-Gross ...
... has been the laser-pellet fusion ... PLASMAS(PHYSICS), *LASERS, *PARAMETRIC INSTABILITY ... Subject Categories : PLASMA PHYSICS AND ...
Stimulated Brillouin scattering, filamentation, and induced Thomson scattering are studied for a coherent electromagnetic plane wave propagating in a uniform plasma. A generalized Green's function is found that describes the impulse response for stimulated scattering by electron and ion modes. Explicit asymptotic Green's functions are calculated for those ...
Parametric resonance in an inhomogeneous plasma is analyzed. Expressions are obtained for the threshold fields for apseriodic instabilities and for ion-acoustic instabilities. It is shown that the threshold for the exditation of periodic instabilities is much higher in a plasma with hot ions. (auth)
Several detrimental instabilities can be excited when a high-intensity laser interacts with plasma. The temporal evolution and spectra of the scattered light emitted by many of these instabilities are used to characterize the instabilities and to benchmark theories. It has been difficult to image the emission region with sufficient ...
... Descriptors : *Ionosphere, *Plasmas(Physics), *Electromagnetic radiation, Instability, Electron density, Ion density, Plasma devices, Modification. ...
... INSTABILITIES IN THE IONOSPHERE EXCITED BY POWERFUL RADIO WAVES OBSERVED OVER ARECIBO, IN: AGARD CP-138, PAPER NO4. ...
The nonlinear saturation of the absolute stimulated Raman scattering (SRS) instability is considered in a finite homogeneous plasma. The amplitude of the incident wave exceeds the absolute instability threshold by the fractional amount delta (
A class of collective three-wave parametric instabilities resulting from the overlap of {ital N}, phase-independent, converging laser beams, each with finite frequency bandwidth and modest spatial incoherence is considered. A statistical analysis is employed based on the random phase approximation (RPA) to derive the thresholds, growth rates, and spatial ...
Results found by applying a predictive model to a particular system (University of Maryland Computer
... CHARGED PARTICLES), LASER BEAMS, ELECTRONS, NONLINEAR SYSTEMS, PARAMETRIC INSTABILITY, KINETICS, RAMAN SPECTRA ...
... Title : Theory and Experiments on Chemical Instabilities. ... relative rates have been calculated and the challenge of predicting absolute rates remains ...
... effect. At low flow speeds a convective instability is found and at higher flow speeds there is an absolute instability. (Author). ...
... obtain numerical estimates of the growth rates for various parameters, and second to identify the instabilities as being either absolute or convective. ...
... One of them, in which the wave grows indefinitely with time, is called absolute instability, and the other, in which the wave grows spatially as it ...
This report shows a detailed analysis of the homogeneous dispersion relation of the parametric instability induced by a Lower Hybrid (LH) pump wave for the plasma parameters typical of the NET/ITER tokamaks. The parametric dispersion relation (PDR) is sol...
Experimental data are presented which shows that during lower hybrid radio frequency heating of the Princeton ATC Tokamak, parametric instabilities are excited, and the ion heating correlates with the presence of the parametric spectra. A theoretical inte...
We consider the effects of a weak ambient magnetic field on the oscillating two stream and parametric decay instabilities, with particular emphasis on the dependence on the angular variation of the instability thresholds and growth rates on the magnetic f...
Parametric instabilities during the ion Bernstein wave (IBW) experiment of plasma heating on PBX-M are investigated both theoretically and experimentally. The theoretical work shows that the RF power threshold of the instabilities is very low when the pla...
Simple general arguments are used to show that for instabilities resulting from the coupling of two weakly damped linear modes with oppositely directed group velocities, such as the various parametric instabilities, there exists a range of coupling streng...
Absolute instabilities of counterpropagating pump beams in a dispersive Kerr medium, placed inside a Fabry{endash}Perot cavity, are analytically studied by use of the analysis and the results of part I [J. Opt. Soc. B {bold 14}, {bold 607} (1998)]. Our approach allows characterization of such a complicated nonlinear system in terms of a doubly resonant ...
The dependence of the threshold value of the field intensity on the wave vector of growing plasma perturbations is studied. The spatial region of development of absolute parametric instability is determined. It is shown that the size of the region is of the order of the size of the plasma corona produced of a laser-irradiated solid ...
... rate. The compressibility of the ambient gas, as well as the surface tension, tends to promote absolute instability. The precise ...
... It is shown that for the absolute instability, the demonstration of Polovin has to be completed to avoid an ambiguity. For ...
... PLASMAS(PHYSICS), *ELECTROMAGNETIC WAVE REFLECTIONS, ELECTROMAGNETIC RADIATION, HEATING, ELECTRON DENSITY ...
It is shown that dust lattice waves (DLWs) become parametrically unstable in a turbulent dusty plasma sheath that contains random-phase ion plasma waves. Physically, the parametric instability arises because of the nonlinear coupling between ion plasma waves and DLWs. The parametric instability ...
Experimental data are presented which show that during lower-hybrid radio-frequency heating of an adiabatic-toroidal-compressor Tokamak, parametric instabilities are excited, and the ion heating correlates with the presence of the parametric spectra. A theoretical interpretation of the parametric ...
The full Raman scattering equations have been solved in a linear density profile in an attempt to overcome the local nature of most previous analyses. The global solution obtained elucidates the transition between absolute and convective Raman instabilities. Feedback linking backward and forward Raman scattering can result in an ...
The purpose of the work reported herein is to examine absolute modes of the TPD instability in two dimensions in an infinite homogeneous plasma. Briggs has shown that the condition for absolute instability in this case is the existence of a solution of th...
A two-layer quasigeostrophic model is used to investigate whether dissipation can induce absolute instability in otherwise convectively unstable or stable background states. It is shown that dissipation of either temperature or lower-layer potential vorticity can cause absolute instabilities over a wide range of ...
We examine the interaction of an electron beam penetrating a strongly correlated plasma. Conditions are established for this unstable interaction to lead to an absolute instability. We propose the absolute instability as a means for probing the strongly correlated plasmas.
The electron-cyclotron drift instability is observed to develop an absolute instability in the laboratory frame of stationary electrons. The authors investigate the threshold, temporal and spatial growth, and the saturation mechanism. (Author)
The Karman vortex street in the wake of a circular cylinder is shown to be due to an absolute instability of the flow in the near wake. A new means of instability analysis is used, involving mappings from the complex k plane to the complex ..omega.. plane.
The basis of undesirable e.ect of parametric oscillatory instability in Fabry-Perot cavity is excitation of the additional (Stokes) optical mode having frequency ?1, and the mirror elastic mode, having frequency ?m. It appears when optical energy stored in the main mode, with frequency ?0, exceeds a certain threshold and the frequencies are related as ?1 ...
The basis of undesirable effect of parametric oscillatory instability in signal recycled LIGO interferometer is the excitation of the additional (Stokes) optical mode and the mirror elastic mode when optical energy stored in the main mode exceeds the certain threshold. We analyze parametric instability in the ...
The nonlinear interaction between three whistler waves is reconsidered. We argue that the squared growth rate of parametric decay instability has to be expressed in a form that is always positive.
The instability of phase oscillations traveling through many parametric resonances is evaluated. Conditions of stability and nonlinear effects are determined. (tr-auth)
It is shown that soliton formation and the resulting plasma heating are nothing more than the description in configuration space of well-known parametric processes and quasi-linear theory.
It is shown that soliton formation and the resulting plasma heating are nothing more than the description in configuration space of well-known parametric processes and quasilinear theory. (GRA)
A study is made of how plasma motion affects the generation of the harmonics (1/2) ..omega../sub 0/, (3/2) ..omega../sub 0/, and 2..omega../sub 0/ arising due to the resonant interaction of plasma waves with a pump wave of frequency ..omega../sub 0/. Intense harmonic generation is observed when there is a high level of Langmuir turbulence in the plasma. Since the parametric ...
... Absolute negative conductance, unstable plasma oscillations and parametric amplificatoin of intense field harmonics destroy these states. ...
... shows that indeed subharmonic effects occur in ... two eigenmodes of a parametric study at two ... to instability of time-periodic separation bubble flows ...
This report contains abstracts on topics in the following areas: parametric instabilities; hohlraum physics; laser plasma physics with short pulses; and rayleigh-taylor instability and hydrodynamics.
Absolute and convective instabilities of spirals are investigated using the continuous and the so-called absolute spectrum. It is shown that the nature of transport, induced by an absolute instability, is determined by spectral data of the asymptotic wave trains. The results are applied to core ...
The effect of secondary wave coupling mechanism on parametric instabilities in plasmas for fusion applications was investigated. Harmonic generation of the low-frequency wave is found to reduce well the reflectivity of Brillouin scattering and to suppress...
Dimensional analysis is used to obtain results on the turbulent state resulting from parametric instabilities of an initially cold plasma. The results include the possibility of an applied magnetic field, multiple ion species, and arbitrary dimensionality. (AIP)
The parametric instabilities of a hot plasma (..nu../sub e/i..SMS+SMS and A..-->..A+SMS. The corresponding properties are also calculated for the induced scattering of Alfven waves by ions. The kinetic approximation is used, and the inhomogeneity of the plasma is ignored.
The coupling of intense laser light with plasmas is a rich field of plasma physics, with many applications. Among these are inertial confinement fusion (ICF), x-ray lasers, particle acceleration, and x-ray sources. Parametric instabilities have been studi...
Parametric electrostatic instabilities in a non-relativistic, stationary plasma excited by a monoenergetic, relativistic electron beam with density sinusoidally modulated along the direction of the beam flow have been theoretically investigated using mult...
The observed dependence of the TEXTOR-94 density limit on global parameters (I, B, P, etc.) and wall conditioning is compared with the predicted density limit parametric scaling of thermal instability theory. It is necessary first to relate the edge param...
The basic linear theory of the parametric instability driven by a pump E sub 0 sin omega sub 0 t oscillating near the electron plasma frequency is reviewed. An expression is derived for the temporal nonlinear development of the fluctuation spectrum of the...
A new kind of parametric instability is observed in a nonuniform plasma in which a resonant rf electric field and a density cavity grow simultaneously through mutual enhancement. The threshold is observed to be virtually zero and the growth rate is linear...
The theory of nonlinear saturation of the parametric decay instability in the weak turbulence limit is developed, and the resulting kinetic equation solved numerically for a variety of cases. These solutions are compared with the results of a series of co...
The existence of a new instability mechanism of a current-carrying plasma which, for a sufficiently long system, may occur after saturation of the two-stream instability is shown. The instability is due to combined asymmetry and nonuniformity of the elect...
Cylindrical liquid jets are inherently unstable and eventually break into drops due to the Rayleigh-Plateau instability, characterized by the growth of disturbances that are either convective or absolute in nature. Convective instabilities grow in amplitude as they are swept along by the flow, while absolute ...
... Abstract : The stability and bifurcation behavior of mechanical systems parametrically ... the lateral vibration instability in rotating shafts subject to ...
... field the motion of nonrelativistic particle is accom- panied by the conservation of its full energy. ... relativistic particles close to resonance seems to ...
... Abstract : In part one, collective plasma phenomena similar to those occurring in the ionosphere upon incidence of intense electromagnetic waves ...
... BIPHASE PROPELLANTS (LIQUID FUEL-GASEOUS OXIDIZER): Investigations were conducted to determine the effects of (1) both the air and ...
... Title : MODIFIED ELECTRON DISTRIBUTION FUNCTION DURING PARAMETRIC INSTABILITIES, IN: AGARD CP-138, PAPER NO10. ...
We discuss the importance of accurate numerical calculation of elastic modes in the mirrors with suspension �ears� in advanced LIGO interferometer to enable precise predictions of parametric oscillatory instability problem. We show that �ears� of test masses produce additional shift of elastic modes frequencies which is larger than relaxation rate ...
The effect of magnetic shear on electrostatic Bernstein waves is investigated. It is shown that shear leads to nonlocal eigensolutions and the convective damping of the Bernstein waves. The threshold for the parametric instability of a magnetosonic wave into two Bernstein waves in a multispecies plasma is increased by shear. For a magnetosonic heating ...
Experimental data are presented which show that during lower-hybrid, radio-frequency heating of the Princeton University adiabatic toroidal compressor tokamak, parametric instabilities are excited, and the ion heating correlates with the presence of the parametric spectra. A theoretical interpretation of the ...
Parametric instabilities of a circularly polarized Alfven wave in a multispecies magnetized plasma are considered. An analytic kinetic description and hybrid simulations for the linear behavior of the instabilities are given. It is found that, even for low-{beta} regimes, both the kinetic effects and the presence of heavy ions ...
absolute instability disappeared at all locations establishing buoyancy as the primary instability mechanism in self-excited low-density jets.
Absolute SMBS instability has been observed in a plasma and, in contrast to convective instability, contributes to anomalous heating of the plasma. (AIP)
The problem of convective and absolute instability in the interactions of charged particle beams with plasma and with each other was analyzed. (R.V.J.)
... Abstract : Absolute instability of (Gortler vortices on the severely curved concave pressure side of a gas-turbine blade is the main thrust of the third ...
... As water density ratio in one atmospheric pressure in room tern- ... mode of the jet instability. ... 'A Bers, Handbook of Plasma Physics (North-Holland ...
We present the analysis of a nonlinear effect of parametric oscillatory instability in power recycled LIGO interferometer with Fabry-Perot cavities in the arms. The basis for this effect is the excitation of the additional Stokes optical mode and the mirror elastic mode when the optical energy stored in the main Fabry-Perot cavity mode exceeds the certain ...
The basis of undesirable effect of parametric oscillatory instability in signal recycled LIGO interferometer is the excitation of the additional (Stokes) optical mode, with frequency ?, and the mirror elastic mode, with frequency ?, when optical energy stored in the main mode, with frequency ?, exceeds the certain threshold and the frequencies are related ...
Dynamical mechanisms underlying the equilibration of absolute instability are examined in a nonlinear, quasigeostrophic, two-layer model. The key to understanding the nonlinear equilibration is in recognizing that linear absolute instabilities can be stabilized by a reduction of the vertical shear and by ...
Two aspects of the stability of a compressible mixing layer: Absolute/Convective instability and the convective Mach number were considered. It was shown that, for Mach numbers less than one, the compressible mixing layer is convectively unstable unless t...
The critical current, oscillation frequency, and characteristic wave number for the excitation of absolute instability in gyropeniotron amplifiers are calculated from the linear dispersion relation by following the Briggs--Bers criterion. Numerical results are presented for some cases of interest.
Contrary to previous theoretical predictions, it is shown that the dissipative drift-wave instabilities are absolute in tokamak plasmas. The existence of unstable eigenmodes is shown to be associated with a new eigenmode branch induced by the finite toroidal couplings.
The absolute and convective instability of a viscous liquid emanating into a viscous gas in a vertical pipe is analyzed in a parameter space spanned by the Reynolds number, the Froude number, the Weber number, the viscosity ratio, the density ratio, and t...
The absolute and convective instability of a jet of an inviscid compressible fluid emanating into another inviscid compressible fluid is investigated. It is shown that the compressibility of the ambient fluid, as well as the surface tension, tends to prom...
Contrary to previous theoretical predictions, it is shown that the dissipative drift-wave instabilities are absolute in tokamak plasmas. The existence of unstable eigenmodes is shown to be associated with a new eigenmode branch induced by the finite toroi...
We present analytical and numerical work which indicates that during ionospheric heating with high-powered hf radio waves, the oscillating two-stream instability may dominate the parametric decay instability. The oscillating two-stream instability saturat...
There is an important change in the nature of the parametric instability of a plasma when there is a cold-electron impurity in it. Under certain conditions, the instability can occur only if these cold electrons are present. The effect of the high temperatures of hot electrons on the plasma stability of discussed. (AIP)
Various combustion problems related to high frequency instability in liquid rocket engines were studied. Using the steady-state and instability computer programs developed under this study, a parametric investigation was conducted. This investigation dete...
Experiments are reported on the ion thermal transport due to the ion-temperature- gradient-driven instability (ITG mode) and its transport scaling properties with respect to instability parameters like fluctuation level [ital [tilde n
This study is devoted to the laser finite band with effects on the stimulated Raman and Brillouin backscattering, and to the laser spatial incoherence upon the growth of the filamentation instability. The possible reduction of the latter instabilities ini...
Studies of stimulated Raman scattering (SRS) based on the one-dimensional Zakharov--Maxwell equations for homogeneous, finite plasmas are presented for a wide range of parameters relevant to current laser--plasma interaction experiments. It was found that the primary mechanism responsible for saturation of SRS is the parametric decay instability (PDI) of ...
Parametric amplification in nanomechanical structures is demonstrated by modulating a purely intrinsic mechanical parameter of the system-the stress-via piezoelectric electromechanical coupling. Large resonance amplitude and quality factor enhancement due to parametric pumping are observed under both vacuum and ambient pressure conditions. Exploration of ...
The classification of absolute and convective instability is important for the ... one unstable normal mode and the growth rate is uniformly bounded � the ...
High accuracy absolute fields utilize advanced processing techniques. ... scale instabilities. AC Electric Field. ELF Waveforms ...
... The stability of the system is analysed using a causal approach which is able to distinguish between absolute and convective instabilities. ...
... mechanics and aerospace sciences: (1) Flow Control, (2) Chaos and universality in wakes behind circular cylinders, (3) Absolute instability and ...
... The micro-instability is absolute and develops fastest for a critical perturbation wavelength, of the order of several times the thickness of the plasma ...
... These premixed flamelets are quite weak in that ... of a regular subsonic neutral mode was ... absolute instability becomes progressively weaker in that ...
... to four types of interaction which leads to evanescent waves, simple propagating waves, growing waves, and also to an absolute instability. ...
... (2) Understanding the effects of controlled three- dimensional disturbance on the region of absolute instability. Comparison ...
Monsoon depressions over the Bay of Bengal develop almost entirely in July and August. After studies
... It is shown that the gas density has the effect of raising ... LIQUID JETS, *STABILITY, RATIOS, CAPILLARY TUBES, GASES, VISCOSITY, REYNOLDS ...
The wide variety of physical effects accompanying the parametric decay instability driven by the frequency modulated pump is studied experimentally and theoretically. It is shown that pump frequency modulation does not influence the instability when the modulation frequency is much faster than the decay wave transient time in the ...
A theoretical model for the instability of two-dimensional turbulent boundary layer over compliant surfaces is described. The principal Reynolds stress is modelled by a well-established mixing-length eddy-viscosity formulation of van Driest. The perturbations of the mean velocity and Reynolds stress fields are coupled via the turbulence model. The investigation of ...
The undesirable effect of parametric oscillatory instability in a LIGO (Laser Interferometer Gravitational-Wave Observatory) laser gravitational-wave antenna with a signal-recirculation mirror is analysed in detail. The instability is manifested in excitation of the Stokes optical mode and elastic mechanical mode of the mirror. It is ...
The stability of a viscous film flowing down a vertical fiber under the action of gravity is analyzed both experimentally and theoretically. At large or small film thicknesses, the instability is convective, whereas an absolute instability mode is observed in an intermediate range of film thicknesses for fibers of small enough radius. ...
The capillary instability of an infinitely long jet with respect to temporally growing disturbances was analyzed by Rayleigh. Keller et al. examined the capillary instability of a semi-infinite jet with respect to spatially growing disturbances. They foun...
Using multiple time scale analysis, the nonlinear saturation of the absolute stimulated Raman scattering instability is examined in a finite homogeneous collisional plasma. The amplitude of the incident wave is assumed to exceed the absolute instability threshold by the fractional amount ..delta..(<<1). A ...
An electromagnetic device, acting like a spring with alternating stiffness, has been designed to parametrically excite the cantilever beam. However, only one parametric excitation (induced by one electromagnetic device) was considered in current research, and the effects of the design parameters of the device upon the instability were ...
Thresholds and linear growth rates for stimulated Brillouin and Raman scattering and for the parametric decay instability are derived by using arguments of energy transfer. For this purpose an expression for the ponderomotive force is derived. Conditions under which the partial pressure force due to differential dissipation exceeds the ponderomotive force ...
The parametric decays of a lower hybrid (LH) pump are studied in a wide range of low-frequency quasi-modes which drive the instabilities. The numerical results of the parametric dispersion relation show that an ion-sound quasi-mode with frequency omega/su...
Two mechanisms for the excitation of plasma oscillations in the ionosphere during the radio sounding of the ionosphere by the Alouette and Isis satellites are analyzed: the mechanism proposed by Benson (1974) associated with the Harris plasma instability, and the mechanism of parametric instability proposed by Palmer and Barrington ...
A survey of parametric instabilities in plasma, and associated particle heating, is presented. A brief summary of linear theory is given. The physical mechanism of decay instability, the purely growing mode (oscillating two-stream instability) and soliton and density cavity formation is presented. Effects ...
The nonlinear saturation of the absolute stimulated Raman scattering (SRS) instability is considered in a finite homogeneous plasma. The amplitude of the incident wave exceeds the absolute instability threshold by the fractional amount (<<1). A single backscattered wave and a single plasma wave grow until ...
The results of comprehensive experimental and theoretical investigations of the last decade are reviewed, revealing a complicated and interesting behavior of nonlinear inhomogeneous wave system. It is shown that the wide variety of physical effects is accompanying the parametric decay instability (PDI) driven by the frequency modulated pump. The experiment ...
We show that the presence of electric charge at the interface of a capillary liquid jet plays a secondary role concerning the onset of an absolute or a convective instability in common operational conditions for cone-jet electrosprays, compared to other factors such as the convective velocity, jet diameter, surface tension ?, density ?, or viscosity ?. ...
The problem of dynamic stability of viscoelastic extremely shallow and circular cylindrical shells with any hereditary properties, including time-dependence of Poisson�s ratio, are reduced to the investigation of stability of the zero solution of an ordinary integro-differential equation with variable coefficients. Using the Laplace integral transform, an integro-differential equation is reduced ...
Viscous flow over discrete or distributed surface roughness has great implications for hypersonic flight due to aerothermodynamic considerations related to laminar-turbulent transition. Current prediction capability is greatly hampered by the limited knowledge base for such flows. To help fill that gap, numerical computations are used to investigate the intricate flow physics involved. An ...
It has been confirmed that the normal mode of a surface wave on a corrugated metal plate can be excited by a sheet electron beam. Two types of instabilities are analyzed numerically. One is the Cherenkov instability between the surface normal mode and the slow-space-charge mode of the electron beam. This instability is possibly ...
Analysis of the synchrotron-betatron coupling in a free-electron laser indicates that the particle motion is susceptible to an instability of a fundamentally different physical character to those examined previously. The domain of this instability, which is of a parametric type and causes an exponential growth of the betatron ...
Analysis of the synchrotron-betatron coupling in a free-electron laser indicates that the particle motion is susceptible to an instability that is of a fundamentally different physical character to those examined previously. The domain of this instability, which is of a parametric type and causes an exponential growth of the betatron ...
Analysis of the synchrotron betatron coupling in a free electron laser indicates that the particle motion is susceptible to an instability which is of a fundamentally different physical character to those examined previously. The domain of this instability, which is of a parametric type and causes an exponential growth of the betatron ...
A study of the parametric decay instabilities during lower hybrid experiment in the ASDEX tokamak is presented. The new grill launcher permits a better control of wave characteristics and therefore a closer comparison with numerical predictions. Direct RF-ions interactions do not occur and a study of the effect of the plasma ...
Experimental results, interpreted by a theoretical model based on the first two hydrodynamic equations, concerning parametric resonance instabilities in argon and neon dc discharges are presented. These instabilities were detected by scattered microwaves in the frequency band 2--40 GHz when the plasma positive column was ...
Experimental and theoretical studies of a new type of parametric instability involving the excitation of ion quasi-modes (due to nonlinear wave- particle scattering) have been carried out when the ''pump'' frequency is near the lower-hybrid frequency. Plasma heating associated with this ...
The parametric excitation of drift-cyclotron waves is analyzed for the case of a slightly inhomogeneous plasma in an alternating electric field at a frequency of the order of the ion gyrofrequency. The relative velocity of the electrons and ions is assumed much lower than the ion thermal velocity. The growth rate and instability thresholds are derived. The ...
By solving the hydrodynamic equations for the parametric instability including mode-coupling terms, we predict the saturation level and turbulent spectrum for the oscillating two-stream instability. Coupling the electron distribution function to the spectrum with the quasilinear diffusion coefficient gives the heating rate and ...
The experimental conditions leading to substantial reduction of the backscattering decay instability threshold in electron cyclotron resonance heating experiments in toroidal devices are analyzed. It is shown that a drastic decrease of threshold is provided by the nonmonotonic behavior of plasma density in the vicinity of magnetic island and poloidal magnetic field ...
Whistler mode wave emissions in the magnetosheath, known as lion roars, are thought to be generated by an electron cyclotron instability. Reported satellite data are used to model a magnetosheath medium where lion roars emissions occurred, and the character, absolute or convective, of the associated electron cyclotron instability is ...
The conditions for absolute and convective instabilities of kink waves in the plasma of a positive column of a gas discharge are determined. There is an important difference between these conditions, because of the anisotropic ambipolar drift of kink perturbations in the electron-drift direction in the longitudinal electric field. This drift arises when ...
A weak-turbulence theory of parametric instabilities in the electron-cyclotron frequency range in ELMO-bumpy-torus plasmas is developed. Parametric turbulence levels of excited modes are evaluated for principal--and second--electron-cyclotron- harmonic-resonance layers. It is shown that short-wavelength parametric ...
The parametric instability of electrostatic waves in a homogeneous cold plasma, in which the electrons can acquire relativistic velocities in the field of the pump wave, is analyzed. An equation is derived which describes the parametric wave excitation without restriction on the amplitude of the external field. The condition for the ...
Nonlinear effects of parametric and of heating type, produced in a plasma under the action of an electric field E0(e exp i(omega)t), are considered in this work in connection with the Tethered Magnetospheric Cloud (TMC) accompanying the Tether Satellite System (TSS). The theoretical results show that these phenomena should appear in the ionosphere at high altitudes Z greater ...
... b of the function g should not be taken into account by the ... areas (dark color refers to high absolute values of the ... 7 shows an example of remeshing. ...
The nonlinear evolution and saturation of parametrically excited lower hybrid waves are studied numerically by solving the corresponding weak turbulence wave kinetic equation. The saturation level and the effective collision frequency nu /sub f/ are obtai...
The dispersion relation is derived for parametric instabilities caused by an intense ion sound wave which couples high and low frequency electrostatic modes of a nonisothermal unmagnetized homogeneous plasma. The phase velocity of the pump wave is between...
The report is a study of the phase behavior of a parametric amplifier when small variations in pumping or varactor biasing occur. Formulas for the phase instability caused by adjacent signals on the amplifier band are also derived. Experimental results ob...
The case of three parametrically coupled and damped oscillators is considered. One (with natural frequency omega sub 0 ) is externally driven at a frequency omega close to the sum ( omega sub 1 + omega sub 2 ) of the other two. In the vicinity of the para...
Pinch-point instability analysis is used to study the effects of finite temperature on the time-asymptotic pulse shapes of electrostatic and electromagnetic two-stream instabilities. Their absolute or convective instability nature is established over the entire regime from instability threshold ...
Filamentation and Brillouin-enhanced four-wave-mixing instabilities caused by the cooperative interaction between two counterpropagating electromagnetic waves are shown to possess larger convective growth rates and smaller absolute instability thresholds than the conventional single-pump instabilities. These ...
We discuss the importance of accurate numerical calculation of elastic modes in the mirrors of Advanced LIGO to enable precise predictions of the problem of parametric oscillatory instability. We propose accuracy estimations through use of analytical solutions based on Chree Lamb modes. Small deviations from cylindrical test mass shape may produce ...
If the initial wave is unstable in the upper half plane Im ..omega..>0 and there are no branch points of the quasiwave number, or if waves traveling in the same direction coalesce at a branch point, the instability is convective. On the other hand, if a branch point k(..omega..) does exist in the upper half-plane Im ..omega..>0, and not all the waves that merge at this ...
A three mode opto-acoustic parametric amplifier (OAPA) is created when two orthogonal optical modes in a high finesse optical cavity are coupled via an acoustic mode of the cavity mirror. Such interactions are predicted to occur in advanced long baseline gravitational wave detectors. They can have high positive gain, which leads to strong parametric ...
... of Technology Cambridge, Massachusetts 02139-4294 ... due to the PDI (parametric decay instability) were ... plasmas, especially in the auroral region. ...
