Dispersion Relation For Ion Acoustic Waves Research Articles

Boundary effects on dispersion relations of ion-acoustic wave and physical properties of overlapping soliton in a plasma waveguide

Taking into account the cylindrical boundary, a theoretical investigation has been made for the low frequency electrostatic waves in an electron-positron-ion plasma waveguide. The dispersion relation of ion-acoustic (IA) wave is obtained, and a predication for the linear interaction phenomenon of small-amplitude cylindrical IA solitons is presented. It is shown that the cylindrical boundary has significant effects on the dispersion property of IA waves, and the frequency for short wave is significantly modified by the plasma parameters. It has also been noted that cylindrical IA solitons add up linearly when they overlap and penetrate through each other, the maximum amplitude of the overlapping soliton is nearly the sum of the individual soliton amplitude, indicating an apparent linear interaction. Furthermore, the relationships between phase delay and kinetic energy of colliding solitons for an axisymetric cylindrical geometry are derived and discussed in detail. The work presented would be useful to enrich the solitons interaction theory in astrophysical and laboratorial plasma situations.

Ion-Acoustic Solitary Waves in a Partially Degenerate Plasma

The propagation of arbitrary amplitude ion-acoustic (IA) solitary waves (SWs) is studied in unmagnetized, collisionless, homogeneous electron-positron-ion (e-p-i) plasmas with finite temperature degeneracy of both electrons and positrons. Starting from a set of fluid equations for classical ions and Fermi-Dirac distribution for degenerate electrons and positrons, a linear dispersion relation for IA waves is derived. It is seen that the wave dispersion is significantly modified due to the presence of positron species and the effects of finite temperature degeneracy of electrons and positrons. In the nonlinear regime, the Sagdeev's pseudopotential approach is employed to study the existence domain and the evolution of nonlinear IA-SWs in terms of the parameters that are associated with the finite temperature degeneracy, the background number densities, and the thermal energies of electrons and positrons. It is found that in contrast to classical electron-ion plasmas both the subsonic and supersonic IA-SWs can exist in a partially degenerate e-p-i plasma.

On Amplification of Ion-Acoustic Mode in Burning Plasma in Presence of Drift Wave Turbulence

Generation of high frequency ion-acoustic wave in burning plasmas is investigated in presence of drift wave turbulence field. Drift wave turbulence is supported by plasma inhomogeneity of a burning plasma. This low frequency wave phenomenon is playing a crucial role in energy exchange process with alpha particles of fusion reactors. Frequency of ion-acoustic wave in burning plasma may be amplified when the accelerated plasma particles transfer their energy to ion-acoustic wave nonlinearly through a modulated field. Considering an ion distribution function for inhomogeneous plasma, we have evaluated fluctuating parts of distribution function due to drift wave turbulence using Vlasov equation. We have also obtained nonlinear fluctuating parts of ion distribution function due to modulated wave as well as nonlinear ion-acoustic wave. We have estimated the growth rate of ion-acoustic wave using nonlinear dispersion relation for ion-acoustic wave.

A kinetic description of ion-acoustic waves in collisional dusty plasma: Effects of grain charge fluctuations

The dispersion relation for ion-acoustic waves in collisional weakly ionized dusty (complex) plasma is formulated with due regard to the grain charge fluctuations. Calculations of the dielectric response function are performed using the Bhatnagar-Gross-Krook kinetic equation. The grain charging currents are described by the Khrapak-Morfill interpolation formula [S. A. Khrapak and G. E. Morfill, Phys. Plasmas 15, 114503 (2008)]. The dependencies of the charging frequencies and effective collision frequencies on dusty plasma parameters are studied in detail. The analysis of the ion-acoustic wave spectrum is presented for the wide range of the ion collisionality for both nonisothermal and isothermal plasmas.

Landau damping of electrostatic modes in nonthermal plasmas

The dispersion relation (DR) and Landau damping of basic electrostatic modes propagating in an electron-ion plasma modeled by a Cairn's distribution with a spectral index α are kinetically investigated. In the high-frequency range, i.e., ω/k>vte, the DR and Landau damping of the electron Langmuir wave (LW) are obtained. In the low-frequency range where vte>ω/k>vti, the DR of ion acoustic wave (IAW) is investigated. The phase velocity and damping of both the Langmuir and the IAWs are shown to be significantly influenced by the nonthermality parameter α.

Solitary waves in a degenerate relativistic plasma with ionic pressure anisotropy and electron trapping effects

The dynamics of obliquely propagating ion-acoustic (IA) waves in the presence of ionic pressure anisotropy and electron trapping effects is studied in a dense magnetoplasma, containing degenerate relativistic trapped electrons and dynamical (classical) ions. By using the plane wave solution, a modified linear dispersion relation for IA waves is derived and analyzed with different limiting cases and various plasma parameters both analytically and numerically. For nonlinear analysis, a reductive perturbation technique is employed to obtain a Zakharov-Kuznetsov equation involving the weakly nonlinear IA excitations. It is shown that the electron thermal correction and ionic pressure anisotropy strongly modify the wave amplitudes and width attributed to weakly nonlinear IA waves. The stability criterion for stable/unstable solitary pulses is also discussed with variations of angle (β) and temperature ratio (σ). A reduction and domain splitting of unstable excitations into sub-domains with stable and unstable potential pulses are pointed out for electron temperature ratio in the range of 0.01 < σ < 0.3 for degenerate relativistic trapped electrons. Moreover, the ionic pressure anisotropy also considerably affects the stability of solitary potentials in the non-relativistic and ultra-relativistic regimes. The obtained results might be useful for understanding the nonlinear dynamics and propagation characteristics of waves in superdense plasmas, in the environments of white dwarfs and neutron stars, where the electron thermal and ionic pressure anisotropy effects cannot be ignored.

Can ion-acoustic waves in plasma be backward waves?

The dispersion relation for ion-acoustic waves in plasma with ion flow has been analyzed. It is shown that these waves may exist (under certain conditions) in the form of backward waves with antiparallel group and phase velocities. The range of ion flow velocities allowing implementation of backward ion-acoustic waves is found.

Nonlinear ion acoustic excitations in relativistic degenerate, astrophysical electron–positron–ion plasmas

AbstractThe dynamics and propagation of ion acoustic (IA) waves are considered in an unmagnetized collisionless plasma, whose constituents are the relativistically degenerate electrons and positrons as well as the inertial cold ions. At a first step, a linear dispersion relation for IA waves is derived and analysed numerically. For nonlinear analysis, the reductive perturbation technique is used to derive a Korteweg–deVries equation, which admits a localized wave solution in the presence of relativistic degenerate electrons and positrons. It is shown that only compressive IA solitary waves can propagate, whose amplitude, width and phase velocity are significantly modified due to the positron concentration. The latter also strongly influences all the relativistic plasma parameters. Our present analysis is aimed to understand collective interactions in dense astrophysical objects, e.g. white dwarfs, where the lighter species electrons and positrons are taken as relativistically degenerate.

Possible ion-acoustic soliton formation in the ionospheric perturbations observed on DEMETER before the 2007 Pu’er earthquake

The data of ionospheric perturbations observed on DEMETER before the 2007 Pu’er earthquake are analyzed. The three-component plasma (ions, electrons and heavy ions) is studied in the fluid concept. The linear dispersion relation for ion-acoustic wave is found in the presence of heavy ions. The nonlinear dynamics is studied for arbitrary amplitude of the wave. The Sagdeev potential is calculated, which shows that solitary structure exists for Mach number within a range defined by the presence of heavy ions. The developed ion-acoustic solitons may be used as precursor for earthquake prediction.

Dispersion relation for ion-acoustic waves

Dispersion relation for ion-acoustic waves