scholarly journals Damping rate of quasiparticles in degenerate ultrarelativistic plasmas

1997 ◽  
Vol 55 (5) ◽  
pp. 3215-3218 ◽  
Author(s):  
Michel Le Bellac ◽  
Cristina Manuel
Keyword(s):  
Damping Rate

Novel features of electromagnetic waves in an isotropic degenerate electron-ion plasma

2021 ◽  
Author(s):  
P. Maryam ◽  
Rozina Chaudhary ◽  
Shahid Ali ◽  
Hassan Amir Shah ◽  
Stefaan Poedts
Keyword(s):  
Nonlinear Interaction ◽  
Electromagnetic Waves ◽  
Tunneling Effect ◽  
Fermi Velocity ◽  
Degenerate Electron ◽  
Linear Dispersion ◽  
Direct Function ◽  
Ion Plasma ◽  
Damping Rate ◽  
Electron Quantum

Abstract Within the framework of kinetic theory, the nonlinear interaction of electromagnetic waves (EMWs) with a degenerate electron-ion plasma is studied to account for the electron quantum mechanical effects. For this purpose, a specific quantum regime is considered, for which the degenerate electron Fermi velocity is assumed to be taken of the order of group velocity of EMWs. This eventually leads to the existence of nonlinear Landau damping rate for the EMWs in the presence of electron Ponderomotive force. The electrons-ion density oscillations may be arisen from the nonlinear interaction of EMWs, leading to a new type of nonlinear Schrödinger equation in terms of a complex amplitude for electromagnetic pump wave. The profiles of nonlinear damping rate reveal that EMWs become less damped for increasing the quantum tunnelling effects. The electrostatic response for the linear electrostatic waves is also investigated and derived a linear dispersion for the ion-acoustic damping rate. The latter is a direct function of electron Fermi speed and does not rely on the Bohm tunneling effect. The obtained results are numerically analyzed for the two microwaves of different harmonics in the context of nonrelativistic astrophysical dense plasma environments, e.g., white dwarfs, where the electron quantum corrections cannot be ignored.

scholarly journals On the Formation Mechanism of the Seasonal Persistence Barrier

2021 ◽  
Vol 34 (2) ◽  
pp. 479-494
Author(s):  
Yishuai Jin ◽  
Zhengyu Liu ◽  
Chengfei He ◽  
Yuchu Zhao
Keyword(s):  
Growth Rate ◽  
North Pacific ◽  
Signal To Noise Ratio ◽  
Ar Model ◽  
The North ◽  
Sst Variability ◽  
Damped System ◽  
Damping Rate ◽  
Noise Forcing ◽  
The Tropical Pacific

AbstractThe mechanism of the seasonal persistence barrier (SPB) is studied in the framework of an autoregressive (AR) model. In contrast to the seasonal variance, whose minimum is modulated mainly by the minimum growth rate or noise forcing, the SPB is caused primarily by the declining growth rate or increasing noise forcing, instead of the minimum/maximum of the growth rate or noise forcing. In other words, the SPB is caused by the declining signal-to-noise ratio (SNR) rather than the weakest SNR. In a weakly damped system, the phase of the SPB is delayed from that of declining SNR by about a season. The mechanism is further applied to explain the observed SST variability in the tropical and North Pacific. For the tropical Pacific, the spring SPB could be caused by the decreasing growth rate from September to March and weak annual mean damping rate, instead of the minimum growth rate in spring. Over the North Pacific, the increasing noise forcing from March to June may lead to the summer SPB. Our mechanism provides a null hypothesis for understanding the SPB of climate variability.

scholarly journals Ion Acoustic Peregrine Soliton Under Enhanced Dissipation

2021 ◽  
Vol 8 ◽  
Author(s):  
Pallabi Pathak
Keyword(s):  
Acoustic Wave ◽  
Negative Ions ◽  
Landau Damping ◽  
Ion Acoustic Wave ◽  
Multicomponent Plasma ◽  
Plasma Device ◽  
Ion Acoustic ◽  
Damping Rate ◽  
Double Plasma Device ◽  
Spatial Damping

The effect of enhanced Landau damping on the evolution of ion acoustic Peregrine soliton in multicomponent plasma with negative ions has been investigated. The experiment is performed in a multidipole double plasma device. To enhance the ion Landau damping, the temperature of the ions is increased by applying a continuous sinusoidal signal of frequency close to the ion plasma frequency ∼1 MHz to the separation grid. The spatial damping rate of the ion acoustic wave is measured by interferometry. The damping rate of ion acoustic wave increases with the increase in voltage of the applied signal. At a higher damping rate, the Peregrine soliton ceases to show its characteristics leaving behind a continuous envelope.

Analysis of Instabilities in Railway Vehicles Employing Operational Modal Analysis

2015 ◽  
Author(s):  
Lara Erviti Calvo ◽  
Gorka Agirre Castellanos ◽  
Germán Gimenez
Keyword(s):  
Numerical Model ◽  
Modal Analysis ◽  
Mode Shape ◽  
Operational Modal Analysis ◽  
Mode Shapes ◽  
Correct Identification ◽  
Unstable Condition ◽  
Static Tests ◽  
Railway Vehicles ◽  
Damping Rate

The application of Operational Modal Analysis (OMA) in the railway sector opens a broad field of opportunities. The validation of the numerical model employed in the design phase is usually performed employing data obtained in static tests. The drawback is that some suspension parameters, such as dampers, only have an influence in the dynamic behavior and not in the static behavior. Because of that, the use of the mode shapes identified from track measurements in combination with the static tests leads to a more accurate validation of the numerical model. Apart from that, most passenger comfort and dynamic problems are associated to slightly damped modes. A correct identification of the modal parameters can be used as a continuous design improvement tool to improve the comfort and dynamic characteristics of future designs. Another valuable application of OMA techniques is the identification of the mode shapes corresponding to instabilities, due to the safety impact that they have. In railway vehicles, instabilities are associated to mode shapes that present a damping rate which decreases with the increase of the running speed. Above a certain speed value, the excitation coming from track cannot be damped by the vehicle and it reaches an unstable condition. This unstable condition leads to high acceleration levels experienced by the passengers and high interaction forces between the wheel and the rail that may lead to safety hazards. The speed above which the vehicle is unstable is known as critical speed, and has to be greater than the maximum speed of the vehicle with a reasonable safety margin. The use of OMA techniques allows identifying the mode shape that causes the instability. This paper presents the application of OMA techniques to measurements performed on a passenger vehicle, in which the speed was increased until the vehicle was unstable. The mode shape that caused the instability was identified as well as its corresponding natural frequency and damping rate.

GAUGE INDEPENDENCE OF THE FERMION DAMPING RATE IN A HOT PLASMA - LANDAU GAUGE VS COULOMB GAUGE

1993 ◽  
Vol 08 (08) ◽  
pp. 739-748
Author(s):  
H. NAKKAGAWA ◽  
A. NIÉGAWA ◽  
B. PIRE
Keyword(s):  
Perturbation Theory ◽  
Gluon Propagator ◽  
Landau Gauge ◽  
Coulomb Gauge ◽  
Leading Order ◽  
Loop Order ◽  
Hard Thermal Loop ◽  
Hot Plasma ◽  
Damping Rate

The damping rate of a heavy muon/quark in a hot QED/QCD plasma is calculated in the Landau gauge to the effective one-loop order in the resummed perturbation theory of Braaten and Pisarski. For both a muon/quark at rest and in an energetic case we obtain to leading order the same result as in the Coulomb gauge. Resummation of hard-thermal loop corrections to the photon/gluon propagator is of key importance for this gauge independence.

scholarly journals Linear theory of electron-plasma waves at arbitrary collisionality

2019 ◽  
Vol 85 (2) ◽  
Author(s):  
R. Jorge ◽  
P. Ricci ◽  
S. Brunner ◽  
S. Gamba ◽  
V. Konovets ◽  
...  
Keyword(s):  
Electron Distribution Function ◽  
Collision Operator ◽  
Plasma Waves ◽  
Electron Plasma ◽  
Coulomb Collision ◽  
Particle Collisions ◽  
Angle Scattering ◽  
Damping Rate ◽  
Coulomb Collision Operator ◽  
Ion Collision

The dynamics of electron-plasma waves is described at arbitrary collisionality by considering the full Coulomb collision operator. The description is based on a Hermite–Laguerre decomposition of the velocity dependence of the electron distribution function. The damping rate, frequency and eigenmode spectrum of electron-plasma waves are found as functions of the collision frequency and wavelength. A comparison is made between the collisionless Landau damping limit, the Lenard–Bernstein and Dougherty collision operators and the electron–ion collision operator, finding large deviations in the damping rates and eigenmode spectra. A purely damped entropy mode, characteristic of a plasma where pitch-angle scattering effects are dominant with respect to collisionless effects, is shown to emerge numerically, and its dispersion relation is analytically derived. It is shown that such a mode is absent when simplified collision operators are used, and that like-particle collisions strongly influence the damping rate of the entropy mode.

FREQUENCY AND DAMPING RATE OF FAST SAUSAGE WAVES

2014 ◽  
Vol 781 (2) ◽  
pp. 92 ◽  
Author(s):  
S. Vasheghani Farahani ◽  
C. Hornsey ◽  
T. Van Doorsselaere ◽  
M. Goossens
Keyword(s):  
Damping Rate
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