Parametric excitation of surface waves in a strongly inhomogeneous plasma

1991 ◽  
Vol 46 (2) ◽  
pp. 299-307 ◽  
Author(s):  
G. Brodin ◽  
J. Lundberg
Keyword(s):  
Growth Rate ◽  
Surface Wave ◽  
Surface Waves ◽  
Parametric Excitation ◽  
Transition Layer ◽  
Low Temperatures ◽  
Thermal Effects ◽  
Inhomogeneous Plasma ◽  
Resonance Region ◽  
Threshold Value

The parametric excitation of surface waves in a warm inhomogeneous plasma is investigated. It is demonstrated that the coupling between the surface wave and plasmons that can be excited in the transition layer must be taken into account. The growth rate and the threshold value for the instability process are calculated. It is also shown that thermal effects are of importance even for very low temperatures, since the plasmons can now propagate out of the resonance region.

Amplification of nonlinear surface waves in an inhomogeneous transition layer

1991 ◽  
Vol 46 (3) ◽  
pp. 459-462 ◽  
Author(s):  
G. Brodin ◽  
O. M. Gradov
Keyword(s):  
Electromagnetic Field ◽  
Surface Wave ◽  
Surface Waves ◽  
Transition Layer ◽  
Variable Depth ◽  
Nonlinear Surface Waves ◽  
Nonlinear Surface

A plasma with a boundary transition layer of variable depth in the presence of a powerful electromagnetic field is considered. It is shown that a displacement of the boundary will grow, and will propagate as a nonlinear surface wave in the direction in which the depth of the transition layer decreases.

scholarly journals Subharmonic resonant excitation of edge waves by breaking surface waves

2017 ◽  
Vol 24 (2) ◽  
pp. 157-165 ◽  
Author(s):  
Nizar Abcha ◽  
Tonglei Zhang ◽  
Alexander Ezersky ◽  
Efim Pelinovsky ◽  
Ira Didenkulova
Keyword(s):  
Surface Wave ◽  
Surface Waves ◽  
Parametric Excitation ◽  
Laboratory Experiments ◽  
Resonant Excitation ◽  
Edge Waves ◽  
Parametrically Excited ◽  
Subcritical Instability ◽  
Parametric Generation ◽  
Wave Parameters

Abstract. Parametric excitation of edge waves with a frequency 2 times less than the frequency of surface waves propagating perpendicular to the inclined bottom is investigated in laboratory experiments. The domain of instability on the plane of surface wave parameters (amplitude–frequency) is found. The subcritical instability is observed in the system of parametrically excited edge waves. It is shown that breaking of surface waves initiates turbulent effects and can suppress the parametric generation of edge waves.

The anharmonic attenuation of surface waves on crystals at low temperatures

1970 ◽  
Vol 320 (1541) ◽  
pp. 175-186 ◽  
Keyword(s):  
Experimental Data ◽  
Surface Wave ◽  
Surface Waves ◽  
General Formula ◽  
Attenuation Coefficient ◽  
Transverse Wave ◽  
Low Temperatures ◽  
Simplified Model ◽  
Integral Expression ◽  
Good Agreement

A general formula for the attenuation of a surface wave by interaction with thermal phonons at low temperatures is given and compared with the results of Maradudin & Mills (1968) for a simplified model. It is argued that the attenuation coefficient will often be qualitatively similar to that of the slow transverse wave propagating in the same direction. Approximations to our integral expression for the attenuation coefficient are discussed and numerical calculations for quartz described in detail. Good agreement with the experimental data of Salzmann, Plieninger & Dransfeld (1968) is obtained.

Absorption and transformation of electrostatic surface waves in the transition layer of a magneto-active plasma

1973 ◽  
Vol 9 (1) ◽  
pp. 33-47 ◽  
Author(s):  
V. V. Demchenko† ◽  
K. E. Zayed
Keyword(s):  
Surface Wave ◽  
Surface Waves ◽  
Transition Layer ◽  
Plasma Layer ◽  
Initial Perturbation ◽  
Active Plasma ◽  
Natural Hybrid ◽  
Plasma Oscillations ◽  
Damping Coefficients ◽  
Plane Plasma

We investigate electrostatic surface-wave damping in strongly inhomogeneous magneto-active plasma with collisions. We demonstrate that such damping occurs at wave frequencies close to the natural (hybrid) frequencies of the plasma oscillations. We obtain dispersion equations and expressions for the damping coefficients of surface waves propagating along (i) the interface of semi-infinite plasmas, (ii) a plane plasma layer, and (iii) a vacuum layer in the plasma. We also study the linear transformation of surface waves into longitudinal oscillations (concentrated in the transition layer and directed along the gradient of plasma density) caused by the initial perturbation.

scholarly journals Subharmonic resonant excitation of edge waves by breaking surface waves

2016 ◽  
Author(s):  
Nizar Abcha ◽  
Tonglei Zhang ◽  
Alexander Ezersky ◽  
Efim Pelinovsky ◽  
Ira Didenkulova
Keyword(s):  
Surface Wave ◽  
Surface Waves ◽  
Parametric Excitation ◽  
Laboratory Experiments ◽  
Resonant Excitation ◽  
Edge Waves ◽  
Parametrically Excited ◽  
Subcritical Instability ◽  
Parametric Generation ◽  
Wave Parameters

Abstract. Parametric excitation of edge waves with a frequency two times less than the frequency of surface waves propagating perpendicular to the inclined bottom is investigated in laboratory experiments. The domain of instability on the plane of surface wave parameters (amplitude–frequency) is found. The subcritical instability is observed in the system of parametrically excited edge waves. It is shown that breaking of surface waves initiates turbulent effects and can suppress the parametric generation of edge waves.

The effect of gradients of density and static magnetic field on the propagation of surface waves and on wave–beam interaction

1973 ◽  
Vol 10 (3) ◽  
pp. 359-369 ◽  
Author(s):  
V. V. Demchenko ◽  
N. M. El-Siragy ◽  
A. M. Hussein
Keyword(s):  
Magnetic Field ◽  
Surface Wave ◽  
Surface Waves ◽  
Static Magnetic Field ◽  
Natural Frequencies ◽  
Propagation Constant ◽  
Inhomogeneous Plasma ◽  
Particle Beam ◽  
Charged Particle Beam ◽  
Axial Density

The propagation of slow surface waves in an inhomogeneous plasma is investigated. Both ‘axial’ and ‘radial’ density gradients n(r) and those of the static magnetic field B0 are taken into account. It is demonstrated that the axial in- homogeneities n(z) and B0(z) result in the dependence of the natural surface- wave frequencies on the ‘axial’ co-ordinate z. The dependence ωSW(z) affects the phase velocity νph = ωswsol;K where K iS the propagation constant. So, in the case of surface-wave excitation by a charged particle beam in an ‘axially’ inhomogeneous plasma, the Cherenkov resonance ωSW= KV0 between the beam and the surface waves breaks, thereby reducing the growth rate of unstable oscillations. This phenomenon might be considered as the stabilization of the beam by the ‘axial’ density gradient. It is also shown that the ‘radial’ gradients n0(r) and B0(r) essentially affect the surface-wave natural frequencies as well. Dispersion equations, expressions for the natural frequencies and growth rates are obtaind, taking into account the gradients of the density and the static magnetic field.

Guided Surface Waves on an Elastic Half Space

1971 ◽  
Vol 38 (4) ◽  
pp. 899-905 ◽  
Author(s):  
L. B. Freund
Keyword(s):  
Wave Propagation ◽  
Surface Wave ◽  
Surface Waves ◽  
Half Space ◽  
Body Wave ◽  
Three Dimensional ◽  
Elastic Half Space ◽  
Normal Displacement ◽  
Rigid Barrier ◽  
Wave Disturbances

Three-dimensional wave propagation in an elastic half space is considered. The half space is traction free on half its boundary, while the remaining part of the boundary is free of shear traction and is constrained against normal displacement by a smooth, rigid barrier. A time-harmonic surface wave, traveling on the traction free part of the surface, is obliquely incident on the edge of the barrier. The amplitude and the phase of the resulting reflected surface wave are determined by means of Laplace transform methods and the Wiener-Hopf technique. Wave propagation in an elastic half space in contact with two rigid, smooth barriers is then considered. The barriers are arranged so that a strip on the surface of uniform width is traction free, which forms a wave guide for surface waves. Results of the surface wave reflection problem are then used to geometrically construct dispersion relations for the propagation of unattenuated guided surface waves in the guiding structure. The rate of decay of body wave disturbances, localized near the edges of the guide, is discussed.

Parametric excitation in an inhomogeneous plasma

1971 ◽  
Vol 5 (1) ◽  
pp. 107-113 ◽  
Author(s):  
C. S. Chen
Keyword(s):  
Electric Field ◽  
Parametric Excitation ◽  
Growth Rates ◽  
Inhomogeneous Plasma ◽  
Electron Plasma ◽  
Transverse Waves ◽  
Circularly Polarized ◽  
Polarized Waves ◽  
Oscillating Electric Field ◽  
Unmagnetized Plasma

An infinite, inhomogeneous electron plasma driven by a spatially uniform oscillating electric field is investigated. The multi-time perturbation method is used to analyze possible parametric excitations of transverse waves and to evaluate their growth rates. It is shown that there exist subharmonic excitations of: (1) a pair of transverse waves in an unmagnetized plasma and (2) a pair of one right and one left circularly polarized wave in a magnetoplasma. Additionally, parametric excitation of two right or two left circularly polarized waves with different frequencies can exist in a magnetoplasma. The subharmonic excitations are impossible whenever the density gradient and the applied electric field are perpendicular. However, parametric excitation is possible with all configurations.

Surface wave attenuation of seismic records with the co-core trace transform filter

Geophysics ◽  
2011 ◽  
Vol 76 (6) ◽  
pp. V115-V128 ◽  
Author(s):  
Ning Wu ◽  
Yue Li ◽  
Baojun Yang
Keyword(s):  
Surface Wave ◽  
Surface Waves ◽  
Field Data ◽  
Wave Attenuation ◽  
Seismic Events ◽  
Data Sets ◽  
Transform Domain ◽  
Recent Developments ◽  
Seismic Records ◽  
Trace Transform

To remove surface waves from seismic records while preserving other seismic events of interest, we introduced a transform and a filter based on recent developments in image processing. The transform can be seen as a weighted Radon transform, in particular along linear trajectories. The weights in the transform are data dependent and designed to introduce large amplitude differences between surface waves and other events such that surface waves could be separated by a simple amplitude threshold. This is a key property of the filter and distinguishes this approach from others, such as conventional ones that use information on moveout ranges to apply a mask in the transform domain. Initial experiments with synthetic records and field data have demonstrated that, with the appropriate parameters, the proposed trace transform filter performs better both in terms of surface wave attenuation and reflected signal preservation than the conventional methods. Further experiments on larger data sets are needed to fully assess the method.

Estimates of Surface Waves Using Subsurface EM-APEX Floats under Typhoon Fanapi 2010

2018 ◽  
Vol 35 (5) ◽  
pp. 1053-1075 ◽  
Author(s):  
Je-Yuan Hsu ◽  
Ren-Chieh Lien ◽  
Eric A. D’Asaro ◽  
Thomas B. Sanford
Keyword(s):  
Surface Wave ◽  
Surface Waves ◽  
Wave Spectrum ◽  
Nonlinear Least Squares ◽  
Peak Frequency ◽  
Wave Propagation Direction ◽  
Model Studies ◽  
Surface Wave Propagation ◽  
Left Quadrant ◽  
Field Inclination

AbstractSeven subsurface Electromagnetic Autonomous Profiling Explorer (EM-APEX) floats measured the voltage induced by the motional induction of seawater under Typhoon Fanapi in 2010. Measurements were processed to estimate high-frequency oceanic velocity variance associated with surface waves. Surface wave peak frequency fp and significant wave height Hs are estimated by a nonlinear least squares fitting to , assuming a broadband JONSWAP surface wave spectrum. The Hs is further corrected for the effects of float rotation, Earth’s geomagnetic field inclination, and surface wave propagation direction. The fp is 0.08–0.10 Hz, with the maximum fp of 0.10 Hz in the rear-left quadrant of Fanapi, which is ~0.02 Hz higher than in the rear-right quadrant. The Hs is 6–12 m, with the maximum in the rear sector of Fanapi. Comparing the estimated fp and Hs with those assuming a single dominant surface wave yields differences of more than 0.02 Hz and 4 m, respectively. The surface waves under Fanapi simulated in the WAVEWATCH III (ww3) model are used to assess and compare to float estimates. Differences in the surface wave spectra of JONSWAP and ww3 yield uncertainties of <5% outside Fanapi’s eyewall and >10% within the eyewall. The estimated fp is 10% less than the simulated before the passage of Fanapi’s eye and 20% less after eye passage. Most differences between Hs and simulated are <2 m except those in the rear-left quadrant of Fanapi, which are ~5 m. Surface wave estimates are important for guiding future model studies of tropical cyclone wave–ocean interactions.

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