共查询到20条相似文献，搜索用时 125 毫秒
1.
H. G. Abdelwahed 《Astrophysics and Space Science》2012,341(2):491-500
Using the Viking Satellite observations data in the dayside auroral zone, a theoretical investigation is carried out for contribution of the higher-order nonlinearity to nonlinear obliquely electron-acoustic solitary waves (EASWs) in a magnetized collisionless plasma consisting of a cold electron fluid and non-thermal hot electrons obeying a non-thermal distribution, and stationary ions. A Zakharov–Kuznetsov (ZK) equation that contains the lowest-order nonlinearity and dispersion is derived from the lowest order of perturbation and a linear inhomogeneous (ZK-type) equation that accounts for the higher-order nonlinearity and dispersion is obtained. A stationary solution for equations resulting from higher-order perturbation theory has been found using the renormalization method. The effects of the external magnetic field and the obliqueness are found to significantly change the higher-order properties (viz. the amplitude, width, electric field and energy) of the EASWs. The effect of higher-order nonlinearity on the amplitude and width of the soliton are also discussed. A comparison with the Viking Satellite observations in the dayside auroral zone are taken into account. 相似文献
2.
The nonlinear propagation of ion acoustic waves in ideal plasmas consisting of degenerate electrons and positrons, and isothermal ions is investigated. The Korteweg de Vries (K-dV) equation that contains the lowest order nonlinearity and dispersion is derived from the lowest order of perturbation and a linear inhomogeneous (K-dV type) equation that accounts for the higher order nonlinearity and the dispersion relation is obtained. The stationary wave solution for these equations has been found using the renormalization method. Also, the effects of electrons and positrons densities and ion temperature on the amplitude and width of solitary waves are investigated, numerically. It is seen that higher order corrections significantly change the properties of the K-dV solitons. Also, it is found that both compressive and rarefactive solitary waves can be propagated in such plasma system. 相似文献
3.
M. Mehdipoor 《Astrophysics and Space Science》2012,338(1):73-79
Korteweg-de-Vries-Burger (K-dVB) equation is derived for ion acoustic shock waves in electron-positron-ion plasmas. Electrons
and positrons are considered superthermal and are effectively modeled by a kappa distribution in which ions are as cold fluid.
The analytical traveling wave solutions of the K-dVB equation investigated, through the (G′/G)-expansion method. These traveling wave solutions are expressed by hyperbolic function, trigonometric functions are rational
functions. When the parameters are taken special values, the shock waves are derived from the traveling waves. It is observed
that the amplitude ion acoustic shock waves increase as spectral index κ and kinematic viscosity η
i,0 increases in which with increasing positron density β and electron temperature σ the shock amplitude decreases. Also, numerically the effect different parameters on the nonlinearity A and dispersive B terms and wave velocity V investigated. 相似文献
4.
S. K. El-Labany E. F. El-Shamy S. A. El-Warraki 《Astrophysics and Space Science》2008,315(1-4):287-295
Nonlinear properties of the dust acoustic (DA) solitary waves in a dusty plasma consisting of negatively variable-charged dust particles, vortex-like distributed ions and two-temperature isothermal electrons are reported. A reductive perturbation theory has been used to derive a modified Korteweg-de Vries (mKdV) equation for the first-order perturbed potential and a linear inhomogeneous mKdV-type equation for the second-order perturbed potential. The renormalization method is used to obtain stationary solutions of these coupled equations. The modifications in the amplitude and width of the solitary wave structure due to the inclusion of two different types of isothermal electrons, external oblique magnetic field, higher-order nonlinearity, and vortex-like distributed ions are investigated. Also a method based on energy consideration was used to obtain the stability condition. Moreover, the numerical results are applied to investigate some nonlinear characteristics of the DA solitary waves. 相似文献
5.
The dielectric tensor, modified plasma dispersion function and dispersion relation for Whistler mode instability in an infinite
magnetoplasma are obtained in the case of cold plasma injection to background hot anisotropic generalized bi-Lorentzian (κ)
plasma in the presence of external perpendicular a.c. electric field. The method of characteristics solutions using perturbed
and unperturbed particle trajectories have been used to determine the perturbed distribution function. Integrals and modified
plasma dispersion function Zκ
*(ξ ) are reduced in power series expansion form. Numerical methods using computer technique have been used to obtained temporal
growth rate for magnetospheric plasma at geostationary height. The bi-Lorentzian (κ) plasma is reducible to various forms
of distribution function by changing the spectral index κ. The results of bi-Lorentzian (κ) plasma are compared with those
of bi-Maxwellian plasma. It has been found that the addition of cold plasma injection gives different frequency spectra. The
a.c. frequency of moderate amplitude increases the growth rate and instability in K space to lower range. Growth rate maximum is not affected by a.c. frequencies. However, it shifts the maximum to lower K space in both cases, rather than on the variation of the magnitude. Thus a physical situation like this may explain emission
of various high frequency whistler emissions by cold plasma injection. The potential application of controlled plasma experiments
in the laboratory and for planetary atmosphere are indicated.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
6.
S. K. El-Labany M. Shalaby R. Sabry L. S. El-Sherif 《Astrophysics and Space Science》2012,340(1):101-108
A theoretical investigation is carried out for understanding the properties of electron-acoustic potential structures (i.e.,
solitary waves and double-layers) in a magnetized plasma whose constituents are a cold magnetized electron fluid, hot electrons
obeying a nonthermal distribution, and stationary ions. For this purpose, the hydrodynamic equations for the cold magnetized
electron fluid, nonthermal electron density distribution, and the Poisson equation are used to derive the corresponding nonlinear
evolution equation; modified Zakharov–Kuznetsov (MZK) equation, in the small amplitude regime. The MZK equation is analyzed
to examine the existence regions of the solitary pulses and double-layers. It is found that rarefactive electron-acoustic
solitary waves and double-layers strongly depend on the density and temperature ratios of the hot-to-cold electron species
as well as the nonthermal electron parameter. 相似文献
7.
Electron-acoustic solitary structures in two-electron-temperature plasma with superthermal electrons
The propagation of nonlinear electron-acoustic waves (EAWs) in an unmagnetized collisionless plasma system consisting of a
cold electron fluid, superthermal hot electrons and stationary ions is investigated. A reductive perturbation method is employed
to obtain a modified Korteweg–de Vries (mKdV) equation for the first-order potential. The small amplitude electron-acoustic
solitary wave, e.g., soliton and double layer (DL) solutions are presented, and the effects of superthermal electrons on the
nature of the solitons are also discussed. But the results shows that the weak stationary EA DLs cannot be supported by the
present model. 相似文献
8.
Mouloud Tribeche Smain Younsi Taha Houssine Zerguini 《Astrophysics and Space Science》2012,339(2):243-247
Arbitrary amplitude dust-acoustic double-layers (DA-DLs) in a plasma with suprathermal electrons, two-temperature thermal
ions, and warm drifting dust grains are investigated. Our results reveal that the spatial patterns of the DA-DLs are affected
by the degree of the electron suprathermality. The electron thermalization involves a decrease of the cold ion component density,
for the existence of localized DA-DLs. An increase of the dust drift velocity requires a decrease of κ (the electron spectral index), for the onset of dust-acoustic double-layers. An increase of the Mach number M leads to an increase of the DL amplitude as well as the corresponding electron spectral index for which the DL occurs. 相似文献
9.
Hamid Reza Pakzad 《Astrophysics and Space Science》2011,333(1):247-255
Ion acoustic shock waves (IASWs) are studied in a plasma consisting of electrons, positrons and ions. Boltzmann distributed
positrons and superthermal electrons are considered in the plasma. The dissipation is taken into account the kinematic viscosity
among the plasma constituents. The Korteweg–de Vries–Burgers (KdV–Burgers) equation is derived by reductive perturbation method.
Shock waves are solutions of KdV–Burgers equation. It is observed that an increasing positron concentration decreases the
amplitude of the waves. Furthermore, in the existence of the kinematic viscosity among the plasma, the shock wave structure
appears. The effects of ion kinematic viscosity (η
0) and the superthermal parameter (k) on the ion acoustic waves are found. 相似文献
10.
Parvin Eslami Marzieh Mottaghizadeh Hamid Reza Pakzad 《Astrophysics and Space Science》2012,338(2):271-278
The head-on collision between two electron-acoustic solitary waves (EASWs) in an unmagnetized plasma is investigated, including
a cold electrons fluid, hot electrons, obeying a nonextensive distribution and stationary ions. By using the extended Poincaré-Lighthill–Kuo
(PLK) perturbation method, the analytical phase shifts following the head-on collision are derived. The effects of the ratio
of the number density of hot electrons to the number density of cold electrons α, and the nonextensive parameter q on the phase shifts are studied. It is found that q and the hot-to-cold electron density ratio significantly modify the phase shifts. 相似文献
11.
A perturbation in the ratio of the matter temperature to the radiation temperature in the form of a Gaussian with amplitude
A and width σ (in units of the redshift z) centered at some redshift z
c is considered, with some “standard” temperature ratio obtained from a simultaneous solution of the cosmological recombination
kinetics and energy equations being taken as the initial (unperturbed) one. Comparatively small (A = ± 0.01), fast (σ = 17) perturbations are shown to give rise to distinct narrow absorption (for A > 0) or emission (for A < 0) quasi-lines in each of the subordinate continua. The positions of these quasi-lines correlate with the position of the
perturbation center, while their intensities are very sensitive to the perturbation amplitude. At the same time, the manifestation
of the perturbation is much less clear in hydrogen lines (subordinate ones and the Ly-α line) and two-photon emission. As a result, the full perturbed spectrum is characterized by the presence of the narrow quasi-lines
mentioned above and by a general decrease (for A > 0) or increase (for A < 0) in intensity with increasing wavelength. 相似文献
12.
S. K. El-Labany R. Sabry W. F. El-Taibany E. A. Elghmaz 《Astrophysics and Space Science》2012,340(1):77-85
The nonlinear ion-acoustic double layers (IADLs) in a warm magnetoplasma with positive-negative ions and nonthermal electrons
are investigated. For this purpose, the hydrodynamic equations for the positive-negative ions, nonthermal electron density
distribution, and the Poisson equation are used to derive a modified Zakharov–Kuznetsov (MZK) equation, in the small amplitude
regime. It is found that compressive and rarefactive IADLs strongly depend on the mass and density ratios of the negative-to-positive
ions as well as the nonthermal electron parameter. Also, it is shown that there are one critical value for the density ratio
of the negative-to-positive ions (ν), the ratio between unperturbed electron-to-positive ion density (μ), and the nonthermal electron parameter (β), which decide the existence of positive and negative IADLs. The present study is applied to examine the small amplitude
nonlinear IADL excitations for the (H+, O2-)(\mathrm{H}^{+}, \mathrm{O}_{2}^{-}) and (H+,H−) plasmas, where they are found in the D- and F-regions of the Earth’s ionosphere. This investigation should be helpful in
understanding the salient features of the nonlinear IADLs in either space or laboratory plasmas where two distinct groups
of ions and non-Boltzmann distributed electrons are present. 相似文献
13.
Nonlinear properties of ion-acoustic (IA) shock are studied by incorporating the effects of electron nonextensivity in a warm electronegative plasma, whose constituents are the inertial positive/negative ions and q-distributed electrons. For this purpose, the evolution equations are solved to obtain Kadomtsev-Petviashvili (KP) Burgers equation by using the reductive perturbation technique and its solution by the tanh method. Furthermore, the conditions for the existence of oscillatory and monotonic shocks are discussed. Numerically, it is found that IA shock propagation characteristics are significantly modified by the variation of plasma parameters, such as, the effects of electron nonextensivity, the positive and negative ion-to-electron temperature ratios (θ i ,θ n ), respectively. The former also affect the dispersion, dissipation and nonlinearity coefficients of the KPB equation involving the IA shocks. The present analyses could be useful for understanding the nonlinear shock wave excitations in space and laboratory plasmas, where two distinct groups of ions are present. 相似文献
14.
Properties of three-dimensional ion-acoustic solitary and shock waves accompining electron-positron-ion magnetoplasma with
high-energy (superthermal) electrons and positrons are investigated. For this purpose, a Zakharov-Kuznetsov-Burgers (ZKB)
equation is derived from the ion continuity equation, ion momentum equation with kinematic viscosity among ions fluid, electrons,
and positrons having kappa distribution together with the Poisson equation. The dependence of the solitary and shock excitations
characteristics on the parameter measuring the superthermality κ, the ion gyrofrequency Ω, the unperturbed positrons-to-ions density ratio ν, the viscosity parameter η, the direction cosine ℓ, the ion-to-electron temperature ratio σ
i
, and the electron-to-positron temperature ratio σ
p
have been investigated. Moreover, it is found that the parameters κ, Ω, ν, η, and ℓ lead to accelerate the particles, whereas the parameters σ
i
and σ
p
would lead to decelerate them. Numerical calculations reveal that the nonlinear pulses polarity are always positive. This
study could be useful to understand the nonlinear electrostatic excitations in interstellar medium. 相似文献
15.
The existence and stability of a test particle around the equilibrium points in the restricted three-body problem is generalized
to include the effect of variations in oblateness of the first primary, small perturbations ϵ and ϵ′ given in the Coriolis and centrifugal forces α and β respectively, and radiation pressure of the second primary; in the case when the primaries vary their masses with time in
accordance with the combined Meshcherskii law. For the autonomized system, we use a numerical evidence to compute the positions
of the collinear points L
2κ
, which exist for 0<κ<∞, where κ is a constant of a particular integral of the Gylden-Meshcherskii problem; oblateness of the first primary; radiation pressure
of the second primary; the mass parameter ν and small perturbation in the centrifugal force. Real out of plane equilibrium points exist only for κ>1, provided the abscissae
x < \fracn(k-1)b\xi<\frac{\nu(\kappa-1)}{\beta}. In the case of the triangular points, it is seen that these points exist for ϵ′<κ<∞ and are affected by the oblateness term, radiation pressure and the mass parameter. The linear stability of these equilibrium
points is examined. It is seen that the collinear points L
2κ
are stable for very small κ and the involved parameters, while the out of plane equilibrium points are unstable. The conditional stability of the triangular
points depends on all the system parameters. Further, it is seen in the case of the triangular points, that the stabilizing
or destabilizing behavior of the oblateness coefficient is controlled by κ, while those of the small perturbations depends on κ and whether these perturbations are positive or negative. However, the destabilizing behavior of the radiation pressure remains
unaltered but grows weak or strong with increase or decrease in κ. This study reveals that oblateness coefficient can exhibit a stabilizing tendency in a certain range of κ, as against the findings of the RTBP with constant masses. Interestingly, in the region of stable motion, these parameters
are void for
k = \frac43\kappa=\frac{4}{3}. The decrease, increase or non existence in the region of stability of the triangular points depends on κ, oblateness of the first primary, small perturbations and the radiation pressure of the second body, as it is seen that the
increasing region of stability becomes decreasing, while the decreasing region becomes increasing due to the inclusion of
oblateness of the first primary. 相似文献
16.
Hamid Reza Pakzad 《Astrophysics and Space Science》2011,334(1):55-60
Ion acoustic shock waves (IASWs) are studied in a plasma consisting of nonextensive electrons and ions. The dissipation is
taken into account the kinematic viscosity among the plasma constituents. The Korteweg-de Vries-Burgers (KdV-Burgers) equation
is derived by reductive perturbation method. Shock waves are solutions of KdV-Burgers equation. It is shown that acceptable
values of q-parameter (where q stands for the electron nonextensive parameter) are more than 3 in a weakly nonlinear analysis. We have found that the amplitude
of shock waves decreases by an increasing q-parameter. 相似文献
17.
The cross-correlation function of solar p modes in a time – distance analysis changes with travel distance (or travel time). The exponential decrease in the amplitude
of the cross-correlation function with travel distance has been interpreted as the dissipation of solar p-mode power and used to determine the lifetimes of high-degree p modes. It is found that the width of the cross-correlation function increases with travel distance. We interpret the increase
in width as the dispersion of the wave packet in a time – distance analysis. The dispersion would also cause a decrease in
amplitude and affect the determination of lifetimes. We include the dispersion effect in the determination of lifetimes of
high-degree p modes in a time – distance analysis and find that the derived lifetime increases significantly compared with the previous
study for degree less than 400. 相似文献
18.
Nonlinear cylindrical fast magnetoacoustic waves are investigated in a dissipative magnetoplasma comprising of electrons,
positrons, and ions. In this regard, cylindrical Kadomtsev-Petviashvili-Burgers (CKPB) equation is derived using the small
amplitude perturbation expansion method. Furthermore, cylindrical Burgers-Kadomtsev-Petviashvili (Cyl Burgers-KP) for a fast
magnetoacoustic wave is derived, for the first time, for spatial scales larger than the electron/positron skin depths, c/ω
p(e,p). Using the tangent hyperbolic method, the solutions of both planar KPB and Burgers-KP equations are obtained and then subsequently
used as an initial profile to solve their respective counterparts in the cylindrical geometry. The effect of positron concentration,
kinematic viscosity, and plasma β are explored both for the KPB and the Burgers-KP shock waves and the differences between the two are highlighted. The temporal
evolution of the cylindrical fast magnetoacoustic wave is also numerically investigated. The present study may be beneficial
to study the propagation characteristics of nonlinear electromagnetic shock waves in planetary magnetospheres. 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.
A theoretical investigation has been made on obliquely propagating dust-ion-acoustic solitary waves (DIASWs) in magnetized
dusty electronegative plasma containing Boltzmann electrons, trapped negative ions, cold mobile positive ions, and arbitrarily
charged stationary dust. The reductive perturbation method has been employed to derive the modified Zakharov-Kuznetsov (MZK)
equation which admits solitary wave solution under certain conditions. The multi-dimensional instability of these solitary
waves is also studied by the small-k (long wavelength plane wave) perturbation-expansion technique. The basic properties (speed, amplitude, width, instability,
etc.) of small but finite amplitude DIASWs are significantly modified by the effects of external magnetic field, obliqueness,
polarity of dust, and trapped negative ions. The implications of our results in space and laboratory plasmas are briefly discussed. 相似文献