Fluctuation-generated Plasma Oscillations

1992

A dispersion relation for a multi-component high-degenerate plasma is investigated by applying the RPA to an idealised system in which carriers are assumed to be free charged particles with isotropic effective mass. The dispersion relation is expanded up to the sixth-order terms in the wave vector and the frequencies of optical and acoustic plasma modes are calculated.

Physical Review

The discussion of electron plasma oscillations is extended to include some of the effects of boundaries. 11 is first shown that an electron taking part in a traveling plasma oscillation will be reflected at a sheath tif infinitesimal thickness with velocity appropriate to the oscillation traveling in the reverse direction. This means that standing waves may be built up without loss at the sheaths. This approach is extended to sheaths v here a finite time of penetration is necessary before reflection occurs and also to the case of reflection at. metallic electrodes. In both cases expressions for the damping are derived and it is concluded that for low pressure discharges damping resulting from imperfect reflection from electrode sheaths may be comparable with collision damping but that damping arising from conducting electrodes is unimportant.

Annals of Physics, 2015

Longitudinal oscillations of the electron fluid in the hydrodynamic model of a metal are examined with pressure effects taken into account. It is well-known that this entails spatial dispersion. The equilibrium electron number density is taken to be non-uniform and a non-self-adjoint fourth order differential equation obeyed by the electric potential is derived. A velocity potential necessary for the description of sound waves is introduced in the standard fashion and the generalized version of Bloch orthogonality appropriate to a non-uniform background is deduced. We observe a duality between electric and velocity potentials in the sense that the respective differential operators are adjoint to each other. The spectrum is calculated in the special case of an exponential profile for the equilibrium electron number density. The surface plasmons are connected with the analytic properties of the scattering amplitude in the complex plane. The phase shift at threshold is expressed in terms of the number of surface plasmon modes via an expression reminiscent of Levinson's statement in quantum mechanics.

Physics Letters A, 2012

Laser produced plasmas Magnetized plasmas Waves and oscillations Effects of magnetic field on the self-consistent oscillatory structures of the laser-blow-off plasma plume are studied using triple Langmuir probe. It is observed that trailing portion of floating potential profile shifted to higher value and this shift also varies with the strength of magnetic field, which is varied from 0 T to 0.15 T. Number of oscillatory structures decreases with increasing the strength of field. It is suggested that the change in density gradient in the presence of magnetic field could be the reason of reduction of oscillating structures.

Physical Review

Division of the first of these equations by the second yields pk q e --q~c oskp+ -p~s inka 2 kp = qadi coskp+smkp i (55) 2 Insertion into Eq. yields 0 = -kq~sinkp 4s.e' pne q~~k sinkP+ m Ug' kp &(~c oskp+sinkp) ) -47' pnl kp 1coskp -sink p 2 nee ( kp -4s'eP ( ] coskP+ sink-P (mVw'E 2 l ) kp 4~ePn& -1 coskPsin-kP-, 2

Journal of Quantitative Spectroscopy and Radiative Transfer, 1990

Some features of plasma oscillations in strongly coupled (nonideal) equilibrium plasmas are investigated. Attention is paid to the character of the plasmon damping, the dispersion relation and the thermal level. Calculations are made of the spectra and the decrements of collisional and nonresonant damping of plasma oscillations. The long-wavelength plasma oscillations turn out to be well-defined in collision-dominated nonideal plasmas. Estimations of the thermal level of plasma oscillations are performed, taking into account welland poorly-defined modes. Due to the relatively high thermal levels, the oscillations can manifest themselves in the properties of strongly coupled plasmas and should also be taken into account in spectral diagnostics of dense plasmas. The results obtained are compared with the available theoretical approximations and both the computer and laboratory experimental data.

Physics of Plasmas, 2014

Intermittent chaos was observed in a glow discharge plasma as the system evolved from regular type of relaxation oscillations (of larger amplitude) to an irregular type of oscillations (of smaller amplitude) as the discharge voltage was increased. Floating potential fluctuations were analyzed by different statistical and spectral methods. Features like a gradual change in the normal variance of the interpeak time intervals, a dip in the skewness, and a hump in the kurtosis with variation in the control parameter have been seen, which are strongly indicative of intermittent behavior in the system. Detailed analysis also suggests that the intrinsic noise level in the experiment increases with the increasing discharge voltage. An attempt has been made to model the experimental observations by a second order nonlinear ordinary differential equation derived from the fluid equations for an unmagnetized plasma. Though the experiment had no external forcing, it was conjectured that the intrinsic noise in the experiment could be playing a vital role in the dynamics of the system. Hence, a constant bias and noise as forcing terms were included in the model. Results from the theoretical model are in close qualitative agreement with the experimental results. V C 2014 AIP Publishing LLC. [http://dx.

Physics of Plasmas, 2015

This paper presents a theoretical model for the transient response of nonlinear coupling between magnetosonic wave and ion acoustic wave in the overdense plasma. Filamentation of magnetosonic wave has been considered to be responsible for magnetic turbulence during the laser plasma interaction. The ion acoustic wave gets excited due to the ponderomotive force exerted by magnetosonic wave and this ion acoustic wave in turn generates perturbation in the background density in the form of spatial density harmonics. Numerical simulation has been carried out for dimensionless coupled equations of magnetosonic wave and ion acoustic wave; and the results show quite complex localized structures that grow with time. The power spectrum has also been studied which shows that the spectral index follows an approximate scaling of the order of $k À2:4 at smaller scales. The data obtained from numerical simulation are used in semi analytical model to better understand the mechanism of nonlinear evolution of magnetosonic wave. The results indicate considerable randomness in the spatial structure of the magnetic field profile which gives sufficient indication of turbulence. V

Communications in Nonlinear Science and Numerical Simulation, 2008

The spectrum of electron phase space density fluctuations of a plasma is calculated by a novel method that parallels conventional calculations of the partition function in statistical physics.

Physical Review Letters, 1997

Radial electron plasma oscillations excited by a laser wake field are measured by frequency domain interferometry. In the nonlinear regime we observe two important effects: (i) an increase of the oscillation frequency and (ii) the damping of the oscillation in a few plasma periods. Simulations show that this last effect is related to the presence of a steep radial density gradient near the focus edge.

Physical Review B, 1996

We show theoretically that strong plasma mode generation is possible in a nonequilibrium steady-state quasi-one-dimensional bounded solid-state plasma, in which a nonequilibrium distribution is maintained by appropriate injection/extraction of carriers. We calculate the density response of realistic model systems using the random-phase approximation, determine the normal modes of the bounded carrier plasma, and show that strong plasma instabilities can be generated under suitable conditions. Such stimulated plasma oscillations could lead to sources of terahertz electromagnetic radiation. ͓S0163-1829͑96͒01135-6͔

Physical Review Letters, 1986

The onset of electromagnetic oscillations that are observed in magnetically confined plasmas~here beams of fast neutrals are injected is associated with the excitation of a mode with poloidal wave number mo 1 and phase velocity equal to the core-ion diamagnetic velocity. The resonant interaction of the mode with the beam ions is viewed as a form of dissipation that allows the release of the mode excitation energy, related to the gradient of the plasma pressure.

Journal of Plasma Physics, 1991

Some properties of the frequency spectrum of magnetic fluctuations in a tokamak two-species plasma are investigated. We start from the nonlinear resistive ballooning kinetic equation. A method based on the fluctuation-dissipation theorem of thermodynamics is employed. The frequency range |ωDe|/ω>|ω*e| is considered. The dependence of magnetic fluctuations on frequency and various macroscopic parameters is discussed. The influence of magnetic fluctuations on plasma thermodynamics is investigated.

2011

We study the frequency of the plasma oscillations of electron-positron pairs created by the vacuum polarization in an uniform electric field with strength E in the range 0.2 E c < E < 10 E c . Following the approach adopted in [1] we work out one second order ordinary differential equation for a variable related to the velocity from which we can recover the classical plasma oscillation equation when E → 0. Thereby, we focus our attention on its evolution in time studying how this oscillation frequency approaches the plasma frequency. The time-scale needed to approach to the plasma frequency and the power spectrum of these oscillations are computed. The characteristic frequency of the power spectrum is determined uniquely from the initial value of the electric field strength. The effects of plasma degeneracy and pair annihilation are discussed.

Journal of Applied Physics, 2008

By focusing a pulsed single mode Nd:YAG laser, we created low temperature plasmas at various pressures with various target gases and collected spectral light emissions to investigate the possibility of turbulent behavior in these types of plasmas. Characteristic fluctuation frequencies, chaotic dimensions, spectral indices, and turbulent fluctuation energies are determined from fluctuations in these spectral light emissions. Values calculated for the spectral index and the chaotic index for each plasma event are found to be within the known values for other turbulent plasma systems. Thus, turbulent fluctuations on a nanosecond time scale are confirmed in the time evolutions of various singly ionized and neutral spectral lines of various gases.