共查询到20条相似文献,搜索用时 15 毫秒
1.
P. K. Shukla 《Astrophysics and Space Science》1985,114(2):381-385
A nonlinear Schrödinger equation is obtained for linearly polarized electromagnetic waves propagating across the ambient magnetic field in an electron-positron plasma. The nonlinearities arising from wave intensity induced particle mass modulation, as well as harmonic generation are incorporated. Modulational instability and localization of pulsar radiation are investigated. 相似文献
2.
《Planetary and Space Science》1994,42(6):507-511
The properties of ion-acoustic waves in steady-state, unmagnetized, dusty plasmas are analyzed using fluid equations. Two damping mechanisms are investigated. The “Tromsø damping” has been discussed in detail by researchers in Tromsø (Havnes et al., Phys. Scr.45, 491, 1992; Melandsø et al., J. geophys. Res.98, 13315, 1993) for dust-acoustic waves, and is related to the fact that a finite phase shift generally exists between the oscillation of the wave potential and the oscillation of the dust grains charge in the presence of the wave. The “creation damping” is due to the continuous injection of fresh ions into the plasma, to replace those which are lost to the dust grains. These fresh ions, produced by ionization of a neutral gas, do not share initially in the wave motion of the pre-existing ions, and thus lower the average momentum of the ion population. 相似文献
3.
The high-energy processes which occur in many astrophysical objects have motivated recent studies (e.g., Tsintsadze and Tsikarishvili, 1976; Ferrariet al., 1978; Sweeney and Stewart, 1978) of large amplitude wave propagation in plasmas. Such investigations are also of interest for laboratory experiments where strong laser radiation interacts with a high-density target. In the present paper we shall show that even rather small amplitude waves in the presence of an external magnetic field can induce particle velocities which are comparable to the velocity of light. In this ultrarelativistic limit we shall demonstrate that two completely new types of circularly polarized waves appear and that under certain conditions, modulational instabilities occur. Finally we look at the possibility to relate the amplitudes and wavelengths of such waves to pulsar data. 相似文献
4.
The nonlinear coupling between a large amplitude electromagnetic wave and the slow background motion in a dusty plasma is considered. Stimulated scattering instabilities are investigated. The relevance of our investigation to cometary and astrophysical plasmas is pointed out. 相似文献
5.
Astrophysics and Space Science - In 1913 Henry N. Russell revealed to the astronomical community a diagram that would revolutionize stellar astronomy. He had plotted the absolute magnitude of field... 相似文献
6.
The problem of nonlinear localized dust acoustic (DA) is addressed in a plasma comprising positive ions, negative ions, and
mobile negatively charged dust grains. We first consider the case when the grain charge remains constant and discuss later
the case when the charge variations are self-consistently included. It is found that a relative increase of the positive ion
density favors the propagation of the DA solitary waves, in the sense that the domain of their admissible Mach numbers enlarges.
Furthermore, electronegativity makes the dust acoustic solitary structure more spiky. When the dust grain charge Q
d
is allowed to fluctuate, the latter is expressed in terms of the Lambert function and we take advantage of this transcendental
function to investigate the variable charge DA solitary wave. Q
d
adopts a localized profile and becomes more negative as the number of charges Z
(−) of the negative ion increases. The dust grains are found to be highly localized. This localization (accumulation) caused
by a balance of the electrostatic forces acting on the dust grains becomes more effective for lower values of Z
(−). An increase of Z
(−) may lead to a local depletion of the negative ions from the region of the soliton’s localization. The results are useful
to understand the salient features of localization of large amplitude dust acoustic waves in cosmic plasmas such as the ionospheric
D-region and the mesosphere. 相似文献
7.
The dynamical properties of electromagnetic (EM) waves in ultra-relativistic electron-positron (EP) plasmas are analytically investigated on the basis of the nonlinear governing equations obtained from a kinetic way. It is shown that the EM wave envelope will collapse and be trapped into a localized region for the modulation interaction with low frequency density variation induced by ponderomotive force. The correlation between the localized strong wave field and the pulsar radio emission is discussed. 相似文献
8.
The nonlinear interaction of the external magnetic field-aligned circularly polarized electro-magnetic radiation with a cold electron-positron plasma is considered. A set of nonlinear equations is derived describing the coupling of the radiation with cold electrostatic oscillations. Modulational instabilities and wave localization are discussed. 相似文献
9.
Interaction of dust acoustic solitary waves in plasmas consisting of medium disorders is investigated. Disorders and inhomogeneities
of the medium are added to the equation of motion as perturbative terms through the medium parameters. The effects of these
perturbations on the behaviour of solitary waves are studied with numerical simulations and the results are compared with
theoretical predictions in a uniform media. 相似文献
10.
I. Ben-Israel T. Piran Aharon Eviatar J. Weinstock 《Astrophysics and Space Science》1975,38(1):125-155
A statistical theory, previously developed for electrostatic waves is extended to the case of electromagnetic waves in the presence of a constant magnetic field. The theory is nonlinear and contains the effects of mode-mode coupling. The extension is not straightforward as assumed previously by many authors and involves calculation of perturbed trajectories in both velocity and configuration space. A diffusion equation is derived for the average particle distribution function, the associated diffusion tensor is calculated and a nonlinear wave dispersion relation is found. All these results contain the usual quasilinear theory as the lowest order approximation. 相似文献
11.
M. J. Miketinac 《Astrophysics and Space Science》1984,106(1):151-160
A numerical method for the solution of the (astrophysical) potential problem is presented. The problem is formulated as a free boundary problem for a mildly nonlinear elliptic partial differential equation and the method is obtained by combining Newton-Raphson's procedure and two different types of discretization. The performance of the method is discussed. 相似文献
12.
The effects of Bohm potential on the head-on collision between two quantum electron-acoustic solitary waves (QEASWs) in two
electron species quantum plasma have been investigated using the extended Poincaré–Lighthill–Kuo (PLK) method. The analytical
phase shifts after the head-on collision of the two QEASWs are derived. Numerically, in two cases (i.e., the dense solid state
plasma and the dense astrophysical environments), the results show that the cold electron-to-hot electron number density ratio,
the quantum corrections of diffraction and Fermi temperature of hot electrons have strong effects on the nature of the phase
shifts and the trajectories of two QEASWs after collision. 相似文献
13.
N. D'Angelo 《Planetary and Space Science》2002,50(4):375-378
The dispersion relation is derived for electrostatic dust-cyclotron (EDC) waves in a collisional plasma with dust grains having both positive and negative charges. The critical electric fields for excitation of two EDC modes in such a plasma are numerically calculated for a laboratory-type plasma. 相似文献
14.
Nonlinear ion acoustic solitary wave structures in electron-positron-ion (e-p-i) magnetized rotating plasmas is studied. The electron and positron species are assumed to be nonthermal and follow the kappa distribution function. The Korteweg de Vries (kdV) equation is derived by employing the reductive perturbation technique for solitary wave in the nonlinear regime. The variation in the amplitude and width of the solitary wave are discussed with the effects of positron concentration, temperature ratio of kappa distributed electrons to positrons, spectral index of the positrons, direction of propagation of the wave with magnetic field and effective gyrofrequency of the rotating nonthermal plasmas. The numerical results are also presented for illustration. 相似文献
15.
Noble P. Abraham Sijo Sebastian G. Sreekala Savithri E. Devi G. Renuka Venugopal Chandu 《Astrophysics and Space Science》2014,349(1):49-55
A popular model of a cometary plasma is hydrogen (H+) with positively charged oxygen (O+) as a heavier ion component. However, the discovery of negatively charged oxygen (O?) ions enables one to model a cometary plasma as a pair-ion plasma (of O+ and O?) with hydrogen as a third ion constituent. We have, therefore, studied the stability of the ion-acoustic wave in such a pair-ion plasma with hydrogen and electrons streaming with velocities $V_{d\mathrm{H}^{+}}$ and V de , respectively, relative to the oxygen ions. We find the calculated frequency of the ion-acoustic wave with this model to be in good agreement with the observed frequencies. The ion-acoustic wave can also be driven unstable by the streaming velocity of the hydrogen ions. The growth rate increases with increasing hydrogen density $n_{\mathrm{H}^{+}}$ , and streaming velocities $V_{d\mathrm{H}^{+}}$ and V de . It, however, decreases with increasing oxygen ion densities $n_{\mathrm{O}^{+}}$ and $n_{\mathrm{O}^{-}}$ . 相似文献
16.
Large-amplitude Alfvén waves propagating along the guide magnetic field in a three-component plasma are shown to be spatially localized due to their nonlinear interaction with nonresonant electrostatic density fluctuations. A new class of subsonic Alfvén soliton solutions are found to exist in the three-component plasma. The Alfvén solitons can be relevant in explaining the properties of hydromagnetic turbulence near the comets. 相似文献
17.
Existence of compressive relativistic solitons is established in an arbitrary ξ-direction, inclining at an angle to the direction of the weak magnetic field (ω
pi
≫ω
Bi
) in this plasma compound with ions, relativistic electrons and relativistic electron beams. It is observed that the absolute
linear growth of amplitudes of compressive solitons is due to inactive role of the weak magnetic field and the initial streaming
speeds of relativistic electrons, electron beams, and Q
b
(ion mass to electron beam mass). Besides, the small initial streaming of electrons is found to be responsible to generate
relatively high amplitude compressive solitons. The non-relativistic ions in the background plasma, but in absence of electron-beam
drift and in presence of weak magnetic field are the causing effect of interest for the smooth growth of soliton amplitudes
in this model of plasma. 相似文献
18.
The nonlinear amplitude modulation of dust-ion acoustic wave (DIAW) is studied in the presence of nonextensive distributed electrons in dusty plasmas with stationary dust particles. Using the reductive perturbation method (RPM), the nonlinear Schrödinger equation (NLSE) which governs the modulational instability (MI) of the DIAWs is obtained. Modulational instability regions and the growth rate of nonlinear waves are discussed. It is shown that the wave characters are affected by the value of nonextensive parameter and also relative density of plasma constituents. 相似文献
19.
A set of three nonlinearly coupled equations governing the interaction between electromagnetic ion-cyclotron and magnetosonic waves is derived. In appropriate limiting cases, the set yields simplified equations. On the other hand, the full set of equations is used to derive a general dispersion relation for the parametric interaction of electromagnetically modulated ion-cyclotron wave packets. An analytical expression for the growth rate of the electromagnetic modulational instability is presented. The relevance of our investigation to non-thermal electromagnetic fluctuations in astrophysical and cometary plasmas is pointed out. 相似文献
20.
Progress in understanding the nonlinear features of dust-acoustic waves (DAWs) which accompany a collisional strongly and weakly coupled unmagnetized dusty plasma with Boltzmann distributed electrons, ions and negatively charged dust grains is presented. By using a hydrodynamic model, the Korteweg–de Vries-Burgers (KdV-Burgers) equation is derived. The existence regions of the solitary pulses are defined precisely. Furthermore, numerical calculations reveal that, due to collisions, the DAWs damp waves and the damping rate of the waves depends mainly on the collision frequency. The collisions are found to significantly change the basic properties of the DAWs. The effects of electron-to-ion concentration ratio, and ion-to-electron temperature ratio have important roles in the behavior of the DAWs. The results may have relevance in space and laboratory dusty plasmas. 相似文献