Scattering of electromagnetic waves by hybrid waves in a two-electron-temperature plasma

1991 ◽  
Vol 46 (1) ◽  
pp. 99-106 ◽  
Author(s):  
S. K. Sharma ◽  
A. Sudarshan
Keyword(s):  
Growth Rate ◽  
Electron Temperature ◽  
High Frequency ◽  
Electromagnetic Waves ◽  
Low Frequency ◽  
Lower Hybrid ◽  
Stimulated Scattering ◽  
Coupled Modes ◽  
Temperature Plasma ◽  
Electrostatic Perturbation

In this paper, we use the hydrodynamic approach to study the stimulated scattering of high-frequency electromagnetic waves by a low-frequency electrostatic perturbation that is either an upper- or lower-hybrid wave in a two-electron-temperature plasma. Considering the four-wave interaction between a strong high-frequency pump and the low-frequency electrostatic perturbation (LHW or UHW), we obtain the dispersion relation for the scattered wave, which is then solved to obtain an explicit expression for the growth rate of the coupled modes. For a typical Q-machine plasma, results show that in both cases the growth rate increases with noh/noc. This is in contrast with the results of Guha & Asthana (1989), who predicted that, for scattering by a UHW perturbation, the growth rate should decrease with increasing noh/noc.

Parametric decay instability of an upper-hybrid wave in a two-temperature plasma

1994 ◽  
Vol 51 (2) ◽  
pp. 193-200 ◽  
Author(s):  
S. Konar ◽  
V. Rai
Keyword(s):  
Growth Rate ◽  
Electron Temperature ◽  
Density Ratio ◽  
Low Frequency ◽  
Lower Hybrid ◽  
Hot Electron ◽  
Hybrid Wave ◽  
Temperature Plasma ◽  
Band Frequency ◽  
Parametric Decay

Parametric decay of an upper-hybrid pump into another upper-hybrid wave and a low-frequency lower-hybrid mode is considered in a two-electron temperature plasma. Expressions for the nonlinear dispersion relation and growth rate are obtained. It is found that the growth rate is quite sensitive to the hot-electron temperature and the density ratio of the hot and the cold components only when the side-band frequency is close to the second or third harmonic of the cyclotron frequency. The relevance of our investigation to Q machines and the ELMO bumpy torus is pointed out.

Quasimode decay of a lower-hybrid wave in a two-electron-temperature plasma

1996 ◽  
Vol 56 (2) ◽  
pp. 237-249
Author(s):  
A. Sudarshan ◽  
S. K. Sharma
Keyword(s):  
Growth Rate ◽  
Electron Temperature ◽  
Decay Channel ◽  
Lower Hybrid ◽  
Hybrid Wave ◽  
Lower Hybrid Wave ◽  
Temperature Plasma ◽  
Parametric Decay ◽  
Cylindrical Plasma ◽  
Ion Cyclotron

We study the quasimode decay of a lower-hybrid wave and a damped ion cyclotron wave in a plasma having two kinds of electrons. This decay channel is also investigated for a cylindrical plasma. The behaviour of the threshold and growth rate with variations in Tn/Tc and non/noc are studied, and a comparison is made with previous results. Our results show that the growth rate and the threshold for the onset of parametric decay are influenced by the presence of the second electron species.

Stimulated scattering of an electromagnetic wave by an upper-hybrid wave in a two-electron-temperature plasma

1989 ◽  
Vol 42 (2) ◽  
pp. 241-246 ◽  
Author(s):  
S. Guha ◽  
Meenu Asthana
Keyword(s):  
Growth Rate ◽  
Electromagnetic Wave ◽  
Electron Temperature ◽  
Concentration Ratio ◽  
Analytical Investigation ◽  
Nonlinear Dispersion ◽  
Hybrid Wave ◽  
Stimulated Scattering ◽  
Temperature Plasma ◽  
Cold Electrons

We present an analytical investigation of the stimulated scattering of an electromagnetic wave by an upper-hybrid wave in a two-electron-temperature plasma using a hydrodynamical model. The nonlinear dispersion equation of the upper-hybrid wave is derived and the growth rate is calculated. It is found that increasing the concentration ratio of hot to cold electrons decreases the growth rate of the upper-hybrid wave.

Nonlinear scattering of whistlers by lower hybrid and ion Bernstein modes

1980 ◽  
Vol 23 (1) ◽  
pp. 141-146 ◽  
Author(s):  
M. S. Sodha ◽  
R. R. Sharma ◽  
V. K. Tripathi
Keyword(s):  
Growth Rate ◽  
Fluid Model ◽  
Whistler Wave ◽  
The Other ◽  
Lower Hybrid ◽  
Nonlinear Scattering ◽  
Stimulated Scattering ◽  
Homogeneous Plasma ◽  
Hybrid Waves ◽  
Lower Hybrid Waves

Following the fluid model for the response of electrons, it is shown that a high-power whistler wave decays efficiently into a lower hybrid or a Bernstein mode and a scattered whistler wave in a homogeneous plasma. The thresholds for these channels of stimulated scattering are generally low. However, the channel of scattering involving lower hybrid waves is possible only for scattering angles exceeding ¼π. The other channel involving Bernstein modes is possible at shorter scattering angles but the growth rate is relatively small and the threshold is high.

Secondary instability of cross-flow vortices in Falkner–Skan–Cooke boundary layers

1998 ◽  
Vol 368 ◽  
pp. 339-357 ◽  
Author(s):  
MARKUS HÖGBERG ◽  
DAN HENNINGSON
Keyword(s):  
Growth Rate ◽  
Shear Layer ◽  
Boundary Layers ◽  
Growth Rates ◽  
High Frequency ◽  
Cross Flow ◽  
Low Frequency ◽  
Secondary Instability ◽  
The Cross ◽  
Flow Vortex

Linear eigenvalue calculations and spatial direct numerical simulations (DNS) of disturbance growth in Falkner–Skan–Cooke (FSC) boundary layers have been performed. The growth rates of the small-amplitude disturbances obtained from the DNS calculations show differences compared to linear local theory, i.e. non-parallel effects are present. With higher amplitude initial disturbances in the DNS calculations, saturated cross-flow vortices are obtained. In these vortices strong shear layers appear. When a small random disturbance is added to a saturated cross-flow vortex, a low-frequency mode is found located at the bottom shear layer of the cross-flow vortex and a high-frequency secondary instability is found at the upper shear layer of the cross-flow vortex. The growth rates of the secondary instabilities are found from detailed analysis of simulations of single-frequency disturbances. The low-frequency disturbance is amplified throughout the domain, but with a lower growth rate than the high-frequency disturbance, which is amplified only once the cross-flow vortices have started to saturate. The high-frequency disturbance has a growth rate that is considerably higher than the growth rates for the primary instabilities, and it is conjectured that the onset of the high-frequency instability is well correlated with the start of transition.

Scattering and Modulational Instabilities in Magnetized Plasmas

1974 ◽  
Vol 29 (12) ◽  
pp. 1736-1741 ◽  
Author(s):  
M. Y. Yu ◽  
K. H. Spatschek ◽  
P. K. Shukla
Keyword(s):  
High Frequency ◽  
Electromagnetic Waves ◽  
Wave Interaction ◽  
Scattered Wave ◽  
Magnetized Plasma ◽  
Stimulated Scattering ◽  
Frequency Wave ◽  
Electrostatic Wave ◽  
Linear Current ◽  
Modulational Instabilities

The decay of a high-frequency wave into a scattered and an electrostatic wave is investigated for a homogeneous magnetized plasma. For wave propagation in arbitrary directions, an equation for the scattered wave is obtained accounting for the effect of the non-linear current density produced by the three-wave interaction process. As an illustration, the propagation of electromagnetic waves perpendicular to the external magnetic field is considered. The growth rates and thresholds for the stimulated scattering and modulational instabilities are obtained. The influence of a weak inhomogeneity is also considered.

On the Dupree–Weinstock turbulence theory

1974 ◽  
Vol 12 (2) ◽  
pp. 177-198 ◽  
Author(s):  
Nelly Peyraud ◽  
Jean Coste
Keyword(s):  
Growth Rate ◽  
High Frequency ◽  
Low Frequency ◽  
Turbulence Theory

We give a necessary criterion of validity for the Dupree–Weinstock theory of turbulence. In this connexion, we analyze two specific cases of high-frequency (HF) and low-frequency (LF) turbulence. In the HF case, we show that an appreciable modification of the growth rate of unstable modes cannot occur before trapping.

Theory of stimulated scattering of large-amplitude waves

2000 ◽  
Vol 64 (4) ◽  
pp. 353-357 ◽  
Author(s):  
L. STENFLO ◽  
P. K. SHUKLA
Keyword(s):  
Growth Rates ◽  
High Frequency ◽  
Large Amplitude ◽  
Electromagnetic Waves ◽  
Long Term Evolution ◽  
Stimulated Scattering ◽  
Term Evolution ◽  
Laboratory Plasmas ◽  
General Dispersion

Comprehensive comments on the theory of stimulated scattering instabilities of high-frequency electromagnetic waves in magnetized plasmas are presented. It is shown that our general dispersion relations are appropriate for deducing valuable information regarding the growth rates of scattering instabilities and the long-term evolution of modulationally unstable waves in space and laboratory plasmas as well as in astrophysical settings.

Turbulent bremsstrahlung instability of whistler mode in the presence of enhanced ion-acoustic fluctuations

1984 ◽  
Vol 31 (3) ◽  
pp. 477-485 ◽  
Author(s):  
S. N. Sarma ◽  
M. Nambu ◽  
S. Bujarbarua
Keyword(s):  
Growth Rate ◽  
Electric Fields ◽  
High Frequency ◽  
Low Frequency ◽  
Resonant Interaction ◽  
Plasma Instability ◽  
Whistler Mode ◽  
Acoustic Fluctuations ◽  
Ion Acoustic ◽  
Nonlinear Force

In the presence of a low-frequency ion-acoustic turbulence and a high-frequency whistler-mode test wave, a new plasma instability occurs owing to a nonlinear force which originates from the resonant interaction between electrons and modulated nonlinear electric fields. The growth rate of the whistler mode is calculated and compared with observations.

Parametric decay in a two-electron-temperature plasma

1990 ◽  
Vol 43 (3) ◽  
pp. 451-456
Author(s):  
S. Guha ◽  
Meenu Asthana
Keyword(s):  
Growth Rate ◽  
Dispersion Relation ◽  
Electron Temperature ◽  
Pump Wave ◽  
Nonlinear Dispersion ◽  
Hybrid Wave ◽  
Temperature Plasma ◽  
Parametric Decay ◽  
Electromagnetic Pump ◽  
Nonlinear Dispersion Relation

Nonlinear decay of an ordinary electromagnetic pump wave into an electro-acoustic wave and an upper-hybrid wave in a two-electron-temperature plasma has been investigated analytically. In contrast with the work of Sharma, Ramamurthy & Yu (1984), it is found that the decay can take place in the absence of the restrictive condition Ti ≫ Te and the plasma be magnetized. Using a hydrodynamical model of the plasma, the nonlinear dispersion relation and growth rate are obtained. A comparison of the present investigation is made with earlier work, and its possible application to the ELMO bumpy torus is discussed.

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