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1.
Electrostatic solitary structures are studied in uniform and nonuniform magnetoplasmas with superthermal electrons. In the linear analysis, the differences in the acoustic frequencies for Maxwellian, Cairns, and Kappa distributed electrons for both homogeneous and inhomogeneous plasmas are highlighted and discussed. It is shown that using the linear dispersion relation, nonlinear Zakharov-Kuznetsov (ZK) equation can be derived both for the homogeneous and inhomogeneous magnetoplasmas. The solution of the ZK equation is presented using the tangent hyperbolic method. It is found that the increasing magnetic field and the angle of propagation enhances the amplitude whereas the increasing number density mitigates the amplitude of the acoustic drift solitary wave. Furthermore, it is observed that the amplitude of the solitary structure is maximum for Cairns, intermediate for Maxwellian, and minimum for the Kappa distributed electrons. The results presented in this paper may be beneficial to understand the formation of electrostatic drift solitary waves in planetary environments where the nonthermal population of electrons are observed by various satellite missions. 相似文献
2.
Weak ion-acoustic solitary waves (IASWs) in unmagnetized plasmas having two-fluid ions and kappa-distributed electrons are considered. The effects of electron suprathermality, warm ion temperature and polarity on the nonlinear properties of these IASWs are analyzed. It is found that our present plasma model may support compressive as well as rarefactive solitary structures. 相似文献
3.
A certain class of non-thermal electron distributions can exhibit more mono-energetic shape and a higher peak than the Maxwellian
distribution. This type of electron distribution can be observed mainly in flaring plasmas. We have studied the influence
of this kind of electron energy distribution on the excitation equilibrium of Fe VIII – Fe XVI in the solar corona. The changes
in synthetic spectra of the emission lines belonging to these ions due to this non-thermal distribution are shown. The possibilities
of finding the shape of the energy distribution function of electrons from the Fe line ratios are also discussed. The results
can be used for diagnostics of coronal plasmas where the deviations of particle energy distributions from the Maxwellian one
can be significant. 相似文献
4.
Our objective here is to investigate a strongly coupled dusty plasma system with the presence of polarization force (PF). This plasma consists of superthermal electrons, Maxwellian ions, and negatively charged dust grains. The nonlinear propagation of dust-acoustic (DA) waves in such dusty plasma system has been theoretically investigated by employing the reductive perturbation method. The Burgers’ and K-dV equations have been derived to and numerically analyzed. It has been found that the dust-acoustic shock and solitary waves exist associated with a negative potential only, and that the effect of the dust fluid temperature significantly modifies the basic properties (amplitude and width) of such nonlinear waves’ potential structures. We hope that the results of our present investigation should help us in understanding the localized electrostatic disturbances in space and laboratory strongly coupled dusty plasmas with superthermal electrons and polarization force. 相似文献
5.
Properties of fully nonlinear ion-acoustic solitary waves in an unmagnetized and collisionless pair-ion (PI) plasma containing superthermal electrons obeying Cairns distribution have been analyzed. A linear biquadratic dispersion relation has been derived, which yields the fast (supersonic) and slow (subsonic) modes in a pair-ion-electron plasma with nonthermal electrons. For nonlinear analysis, Korteweg-de Vries equation is obtained using the reductive perturbation technique. It is found that in case of slow mode, both electrostatic hump and dip type structures are formed depending on the temperature difference between positively and negatively charged ions, whereas, only dip type solitary structures have been observed for fast mode. The present work may be employed to explore and to understand the formation of solitary structures in the space (especially, the Earth’s ionosphere where two distinct pair ion species (H ±) are present) and laboratory produced pair-ion plasmas with nonthermal electrons. 相似文献
6.
Nonlinear propagation of dust-acoustic (DA) waves in a magnetized dusty plasma, consisting of negatively charged mobile dust, Maxwellian ions and two distinct temperature nonextensive electrons (following nonextensive q-distribution each), has been studied and analyzed by deriving and solving the Korteweg-de-Vries (K-dV) equation. According to the outcomes of the investigation, the basic characteristics of the DA solitary profiles are found to be strongly modified by the external magnetic field, nonextensivity of the electrons and the respective number densities of the two species of electrons. The results of this investigation can be applied in both laboratory and astrophysical plasma scenarios for understanding the basic features of the localized electrostatic dust-acoustic solitary waves (DASWs). 相似文献
7.
In recent spacecraft observations, coherent microscale structures such as electrostatic solitary waves are observed in various
regions of the magnetosphere. The Geotail spacecraft observation has shown that these solitary waves are associated with high
energy non-thermal electrons flowing along the magnetic field. The solitary structures are generated as a result of a long
time evolution of coherent nonlinear trapping of electrons as found in bump-on-tail, bi-stream and Buneman instabilities.
It is noted that these solitary waves can be generated at distant regions far away from the spacecraft locations, because
these trapped electrons, or electron holes, are drifting much faster than the local thermal plasmas. Some of the solitary
waves are accompanied by perpendicular electric fields indicating that two-or three-dimensional potential structures are passing
by the spacecraft. Depending on the local plasma parameters, these multi-dimensional solitary structures couple with perpendicular
modes such as electrostatic whistler modes and lower-hybrid modes. In a long time evolution, these perpendicular modes are
dissipated via self-organization of small solitary potentials, leading to formation of one-dimensional potential troughs as
observed in the deep magnetotail. The above dissipative small-scale processes are reproduced in particle simulations, and
they can be used for diagnostics of electron dynamics from spacecraft observation of multi-dimensional solitary waves in various
regions of the magnetosphere.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
8.
A rigorous theoretical investigation is carried out in analyzing the excitation of electrostatic ion acoustic (IA) solitary wave (SW) structures in two dimensional negative ion magneto-plasmas with superthermal electrons (following κ type distribution). The Zakharov-Kuznetsov (ZK) equation is derived by employing the well known reductive perturbation method, and the analytical solution of ZK equation assists to find out the SW profiles along with their properties. The consequences of different plasma parameters (regarding our considered plasma system) variation on SW structures has been studied. It is found that magnetic field intensity, superthermal parameter κ and temperature of positive and negative ions as well as their densities significantly modify the basic characteristics (amplitude, width, etc.) of the SW waves. A comparison of the SW structures is also presented when the electrons are Maxwellian to when they are superthermal. The relevance of the findings of this work with astrophysical plasmas is briefly pointed out. 相似文献
9.
Theoretical investigation is carried out to understand the dynamics and stability of three dimensional ion solitary waves propagating in dense plasma comprising of ultra-relativistic degenerate electrons and positrons and warm ions. A linear dispersion relation is derived which shows a strong dependence of wave on positron concentration (through the change of density balance) and ion-to-degenerate electron temperature ratio. A nonlinear Kadomtsev-Petviashvili equation is derived by employing the reductive perturbation technique and solved analytically and the conditions for existence of stable solitary waves are found. The analysis reveals that only compressive solitary waves exist in the system. Effects of the change of density balance and Fermi temperature ratios are studied in detail, both analytically and numerically. Furthermore, the conditions for stable solitary waves are discussed by using energy consideration method. The numerical results are also presented by using the parameters consistent with the degenerate and ultrarelativistic astrophysical plasmas. 相似文献
10.
A theoretical investigation is carried out to analyse the propagation of ion acoustic (IA) waves in a magnetized bi-ion plasma having two populations of fluid ions and kappa-distributed electrons. The propagation properties of all possible modes (in the linear regime) are investigated. The nonlinear evolution of the IA solitary waves is governed by a Korteweg-de Vries (KdV)-like equation. The influence of obliqueness, magnitude of the magnetic field, ion polarity and electron superthermality on the IA waves is then examined. Our findings should aid in understanding the nonlinear electrostatic excitations that may propagate in spatial magnetized plasmas. 相似文献
11.
Linear dispersion characteristics of the coupled drift acoustic modes are investigated in inhomogeneous dusty magnetoplasmas both when the dust is considered immobile and when the dust dynamics is taken into account in the presence of nonthermal population of electrons and ions. In this regard, Cairns and Kappa distributed electrons and ions are considered. It is found that the nonthermal distributions affect the phase velocities and the fundamental scalelengths of the plasma. It is found that for both the ion and dust dynamics driven waves, the phase velocities are highest for Cairns, intermediate for Kappa, whereas they are minimum for the Maxwellian distributed electrons. The work presented here may be useful to understand the low frequency electrostatic modes in inhomogeneous dusty plasmas such as those found in planetary environments. 相似文献
12.
The combined effects of the obliqueness and nonextensive electrons are incorporated in the study of ion acoustic (IA) waves in a magnetized plasma. The propagation properties of two possible modes (in the linear regime) are investigated. It is found that the electron nonextensivity decreases the phase velocities of both two modes. Also obliqueness leads to increase of separation between two modes. The nonlinear evolution of IA solitary waves is governed by an energy-like equation. The influence of electron nonextensivity, obliqueness and electron population on the existence domain of solitary waves and the soliton characteristics are examined. It is shown that the existence domain of the IA soliton and its profile is significantly depended on the deviation of electrons from thermodynamic equilibrium and obliqueness. Interestingly, the present model supports compressive as well as rarefactive IA solitary waves. Our finding should elucidate the nonlinear electrostatic structures that propagate in astrophysical and cosmological plasma scenarios where nonextensive and magnetized plasma can exist; like instellar plasma stellar polytropes, solar neutrino problem, peculiar velocities of galaxy clusters, dark-matter halos, protoneutron stars, hadronic matter, quark-gluon plasma, and magnetosphere, etc. 相似文献
13.
Biswajit Sahu 《Astrophysics and Space Science》2013,345(2):415-420
A first theoretical work is presented to study the propagation of two-solitons in an electron acoustic waves (EAWs) within the theoretical framework of the Tsallis statistical mechanics. For this purpose, cylindrical and spherical Korteweg-de Vries (KdV) equations are derived for electron acoustic solitary waves (EASWs) in an unmagnetized three species plasma system comprised of cold electrons, immobile ions and hot electrons featuring Tsallis statistics by employing the standard reductive perturbation method. The effects of electron nonextensivity and the fractional number density of the hot electrons relative to that of the cold ones number density (α) on the profiles of two-soliton structures are investigated numerically. Results would be helpful for understanding the localized structures that may occur in space plasmas. 相似文献
14.
H. A. Shah W. Masood M. T. Asim M. N. S. Qureshi 《Astrophysics and Space Science》2014,350(2):615-622
In the present work, we have considered the nonlinear effects due to trapped electrons in an inhomogeneous degenerate quantum plasma. The formation of drift solitary structures has been investigated for both fully and partially degenerate plasmas. The Sagdeev potential approach has been employed to obtain arbitrary amplitude solitary structures. Interestingly, for a fixed value of density, not only compressive but rarefactive solitary structures have been obtained for a certain temperature range. Furthermore, it has been observed that the drift solitary structures exist only for the case when the drift velocity is smaller than the velocity of the nonlinear structure. The theoretical results obtained have been analyzed numerically for the parameters typically found in white dwarfs and the relevance of the results with regard to white dwarf asteroseismology is also pointed out. 相似文献
15.
Propagation of cylindrical and spherical electron-acoustic solitary waves in unmagnetized plasmas consisting of cold electron
fluid, hot electrons obeying a superthermal distribution and stationary ions are investigated. The standard reductive perturbation
method is employed to derive the cylindrical/spherical Korteweg-de-Vries equation which governs the dynamics of electron-acoustic
solitons. The effects of nonplanar geometry and superthermal hot electrons on the behavior of cylindrical and spherical electron
acoustic soliton and its structure are also studied using numerical simulations. 相似文献
16.
In the present investigation, we have studied the linear and nonlinear propagation of electrostatic waves in a dense magnetoplasma with trapped electrons. Using the small amplitude approximation, formation of solitary structures has been studied both for fully and partially degenerate plasmas. The theoretical results obtained have been analyzed numerically for the parameters typically found in white dwarfs. The present work may be beneficial to understand the propagation of solitary structures with weak transverse perturbation with special reference to white dwarf asteroseismology. 相似文献
17.
Hamid Reza Pakzad 《Astrophysics and Space Science》2011,334(2):337-343
Nonlinear ion acoustic solitary waves (IASWs) are addressed in a weakly relativistic plasma consisting of cold ion fluid,
q-nonextensive electron velocity distribution and Boltzmann distributed positron. The Korteweg-de Vries- (KdV) equation is
derived by reductive perturbation method. We investigate the effect of nonextensive electrons on solitary waves in this medium.
It is found that only compressive solitons can be appeared in the existence of nonextensive electrons. It is shown that the
structure of soliton depend sensitively on the q-nonextensive parameter. 相似文献
18.
A theoretical model is presented to investigate the existence, formation, and possible realization of nonlinear envelope ion acoustic solitary waves which accompany collisionless electron-positron-ion plasmas with high-energy electrons and positrons (represented by kappa distribution). By employing the reductive perturbation method, the hydrodynamic model and the Poisson equation are reduced to nonlinear Schr?dinger equation. The effects of the superthermal parameters, as well as ion-to-electron temperature ratio on the propagation and stability of the envelope solitary waves are examined. The superthermal parameters (ion-to-electron temperature ratio) give rise to instability (stability) of the solitary excitations, since the instability window is strongly modified. Finally, the present results should elucidate the excitation of the nonlinear ion-acoustic solitary wave packets in superthermal electron-positron-ion plasmas, particularly in interstellar medium. 相似文献
19.
Hamid Reza Pakzad 《Astrophysics and Space Science》2012,337(1):217-222
The propagation of nonlinear waves in plasmas consisting of cold electron fluid and superthermal hot electrons and stationary
ions is studied. The Korteweg-de Vries (KdV) equation is derived using the reductive perturbation theory. It is found that
only the rarefractive solitons can be created. Moreover, the linear dispersion relation and energy of solitary waves in the
presence of hot superthermal electrons are derived. Our investigation is of wide relevance to astronomers and space scientists
working on interstellar space plasmas. 相似文献
20.
Ion acoustic solitary waves and periodic waves in an unmagnetized plasma with superthermal (kappa distributed) cool and hot electrons have been investigated using non-perturbative approach. We have transformed basic model equations to an ordinary differential equation involving electrostatic potential. Then we have applied the bifurcation theory of planar dynamical systems to the obtained equation and we have proved the existence of solitary wave solutions and periodic wave solutions. We have derived two exact solutions of solitary and periodic waves depending on the parameters. From the solitary wave solution and periodic wave solution, we have shown the effects of density ratio p of cool electrons and ions, spectral index κ, and temperature ratio σ of cool electrons and hot electrons on characteristics of ion acoustic solitary and periodic waves. 相似文献