共查询到20条相似文献，搜索用时 62 毫秒
1.
N. R. Kundu M. M. Masud K. S. Ashrafi A. A. Mamun 《Astrophysics and Space Science》2013,343(1):279-287
A rigorous theoretical investigation has been made on multi-dimensional instability of obliquely propagating electrostatic dust-ion-acoustic (DIA) solitary structures in a magnetized dusty electronegative plasma which consists of Boltzmann electrons, nonthermal negative ions, cold mobile positive ions, and arbitrarily charged stationary dust. The Zakharov-Kuznetsov (ZK) equation is derived by the reductive perturbation method, and its solitary wave solution is analyzed for the study of the DIA solitary structures, which are found to exist in such a dusty plasma. The multi-dimensional instability of these solitary structures is also studied by the small-k (long wave-length plane wave) perturbation expansion technique. The combined effects of the external magnetic field, obliqueness, and nonthermal distribution of negative ions, which are found to significantly modify the basic properties of small but finite-amplitude DIA solitary waves, are examined. The external magnetic field and the propagation directions of both the nonlinear waves and their perturbation modes are found to play a very important role in changing the instability criterion and the growth rate of the unstable DIA solitary waves. The basic features (viz. speed, amplitude, width, instability, etc.) and the underlying physics of the DIA solitary waves, which are relevant to many astrophysical situations (especially, auroral plasma, Saturn’s E-ring and F-ring, Halley’s comet, etc.) and laboratory dusty plasma situations, are briefly discussed. 相似文献
2.
Maxim Lyutikov 《Monthly notices of the Royal Astronomical Society》1998,293(4):447-468
Normal modes of a one-dimensional relativistically streaming electron–positron plasma in a superstrong magnetic field are considered, taking into account possible different bulk velocities and thermal effects. This physical picture corresponds to the plasma present on the open field lines of rotating neutron stars where the observed radio emission is generated. Various cases are considered: relativistic and non-relativistic relative streaming of cold components, and relativistically hot distributions. A distinction between superluminous and subluminous waves (which can be excited by the Cherenkov effect) is clearly stated. In the low-frequency regime the Cherenkov and cyclotron two-stream instabilities occur. Polarization of the quasi-transverse modes changes from circular for the propagation along magnetic field lines to linear for angles of propagation larger than some critical angle that depends on the relative velocity of the plasma components. 相似文献
3.
H. Alinejad 《Astrophysics and Space Science》2012,337(2):637-643
A theoretical investigation is carried out for understanding the basic features of oblique propagation of linear and nonlinear
ion-acoustic waves subjected to an external magnetic field in an electron-positron-ion plasma which consists of a cold magnetized
ion fluid, Boltzmann distributed positron, and electrons obeying a trapped distribution. In the linear regime, two dispersion
curves are obtained. It is shown that the positron concentration causes the both modes to propagate with smaller phase velocities.
Then, owing to the presence of resonant electrons, the modified Korteweg-de Vries equation describing the nonlinear dynamics
of small but finite amplitude ion-acoustic waves is derived. It is found that the effects of external magnetic field (obliqueness),
trapped electrons, positron concentration and temperature ratio significantly modify the basic features of solitary waves. 相似文献
4.
Frank Verheest 《Astrophysics and Space Science》1974,28(1):91-99
The dispersion law for the propagation of waves in cold magnetized plasmas is derived for arbitrary directions of the rotation axis with respect to the static magnetic field. The waves are shown to be stable, not only in the case of a cold plasma, but in any plasma case which yields hermitian mobility tensors. An interesting special case is when the rotation and magnetization axes are parallel, because then for suitable values of rotation and external magnetic field the two effects can cancel each other, though only for one plasma species at the time. The rotation thus decisively affects and shifts the number and width of the existing pass- and stop-bands in a magnetized plasma. The inclusion of thermal effects through a scalar barotropic pressure is not nearly as significant. 相似文献
5.
F.Z. Feygin Ju.P. Kurchashov V.A. Troitskaya D.S. Fligel K. Dobeš 《Planetary and Space Science》1979,27(2):151-158
A method of estimating hot and cold plasma parameters using ground Pc 1 observations is proposed. The values of both hot and cold plasma concentrations, proton energy and temperature anisotropy in the Pc 1 generation region are calculated. It is shown that the most appropriate (effective) indicator of the L-shell, where Pc 1 are generated, is the group delay of wave packets. 相似文献
6.
Making use of the Sagdeev pseudo-potential approach, we derive the energy like equation for dust-acoustic (DA) solitary waves in a complex plasma having negatively charged cold dust, and electrons/ions featuring the Tsallis distribution. The effects of electron and ion nonextensivity on the DA soliton profile are examined. It is shown that depending on the strength of particle nonextensivity, our plasma model may admit compressive as well as rarefactive DA solitary waves. Our results complement previously published results on this problem. 相似文献
7.
Nonlinear dynamics of electron-acoustic solitary waves in a magnetized plasma whose constituents are cold magnetized electron fluid, hot electrons featuring Tsallis distribution, and stationary ions are examined. The nonlinear evolution equation (i.e., Zakharov–Kuznetsov (ZK) equation), governing the propagation of EAS waves in such plasma is derived and investigated analytically and numerically, for parameter regimes relevant to the dayside auroral zone. It is revealed that the amplitude, strength and nature of the nonlinear EAS waves are extremely sensitive to the degree of the hot electron nonextensivity. Furthermore, the obtained results are in good agreement with the observations made by the Viking satellite. 相似文献
8.
S. A. El-Wakil Essam M. Abulwafa E. K. El-Shewy Abeer A. Mahmoud 《Astrophysics and Space Science》2013,346(2):383-393
The reductive perturbation method has been used to derive the Burgers equation for dust acoustic shock waves in unmagnetized plasma having electrons, singly charged ions, hot and cold dust species with Boltzmann distributions for electrons and ions in the presence of the cold (hot) dust viscosity coefficients. The time-fractional Burgers equation is formulated using Euler-Lagrange variational technique and is solved using the variational-iteration method. The effect of time fractional parameter on the behavior of the shock waves in the dusty plasma has been investigated. 相似文献
9.
N. D'Angelo 《Planetary and Space Science》1998,46(11-12)
Electrostatic dust-cyclotron (EDC) waves can be excited in a collisional, magnetized, dusty plasma by passing a current along the magnetic field, B, permeating the plasma. The minimum B field-aligned electric field required for excitation of the EDC waves is typically several times smaller than the one required for excitation of dust-acoustic (DA) waves.Two dusty plasmas are considered in more detail, namely (a) a comet tail plasma, and (b) one which may be produced in a laboratory device of the type described by Xu et al. (1992). 相似文献
10.
A.A. Mamun 《Astrophysics and Space Science》1998,260(4):507-514
A rigorous theoretical investigation has been made of obliquely propagating dust-acoustic solitary structures in a cold magnetized two-ion-temperature dusty plasma consisting of a negatively charged, extremely massive, cold dust fluid and ions of two different temperatures. The reductive perturbation method has been employed to derive the Korteweg-de Vries (K-dV) equation which admits a solitary wave solution for small but finite amplitude limit. It has been shown that the presence of second component of ions modifies the nature of dust-acoustic solitary structures and may allow rarefactive dust-acoustic solitary waves (solitary waves with density dip) to exist in such a dusty plasma system. The effects of obliqueness and external magnetic field on the properties of these dust-acoustic solitary structures are also briefly discussed. 相似文献
11.
We investigate the problem of determining the plasma composition of relativistic jets in blazars and microquasars from the polarization frequency spectra of their synchrotron radiation. The effect of plasma composition on this radiation is attributable to a change in the structure of the ordinary and extraordinary waves in plasma, depending on the presence of a nonrelativistic electron-proton component in it and on the type of relativistic particles (electrons, positrons). The structure of the normal waves determines the properties of the observed radiation and primarily the shape of the polarization frequency spectrum. Our analytic calculations of the polarization spectra for simple models of jets with a uniform magnetic field and with a magnetic-field shear revealed characteristic features in the polarization spectra. These features allow us to differentiate between the synchrotron radiation from an admixture of relativistic particles in a cold plasma and the radiation from a relativistic plasma. However, definitive conclusions regarding the relativistic plasma composition (electrons or electron-positron pairs) can be reached only by a detailed analysis of the polarization frequency spectra that will be obtained in future radioastronomical studies with high angular and frequency resolutions. 相似文献
12.
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
13.
Dean F. Smith 《Astrophysics and Space Science》1976,42(2):261-283
A general scheme is established to examine any magnetohydrodynamic (MHD) configuration for its acceleration potential including the effects of various types of plasma waves. The analysis is restricted to plasma waves in a magnetic field with electron cyclotron frequency less than, but comparable to, the electron plasma frequency (moderate field). The general role of electron plasma waves is examined in this paper independent of a specific MHD configuration or generating mechanism in the weak turbulence limit. The evolution of arbitrary wave spectra in a non-relativistic plasma is examined, and it is shown that the nonlinear, process of induced scattering on the polarization clouds of ions leads to the collapse of the waves to an almost one-dimensional spectrum directed along the magnetic field. The subsequent acceleration of non-relativistic and relativistic particles is considered. It is shown for non-relativistic particles that when the wave distribution has a negative slope the acceleration is retarded for lower velocities and enhanced for higher velocities compared to acceleration by an isotropic distribution of electron plasma waves in a magnetic field. This change in behavior is expected to affect the development of wave spectra and the subsequent acceleration spectrum.The National Center for Atmospheric Research is sponsored by the National Science Foundation. 相似文献
14.
E. F. El-Shamy W. F. El-Taibany E. K. El-Shewy K. H. El-Shorbagy 《Astrophysics and Space Science》2012,338(2):279-285
The characteristics of the head-on collision (HOC) between two positron acoustic solitary waves (PASWs) in a four component
electron-positron-ion (EPI) space plasma have been investigated theoretically, using the extended Poincaré-Lighthill-Kuo (PLK)
method. The analytical phase shifts after the collision of the two solitary waves occurs are derived. Numerically, the influences
of the cold/hot positron parameters on the phase shifts are explicitly investigated. The present theory is applied to analyze
the formation and the interaction of localized coherent PASWs structures in space plasmas (pulsar environments). 相似文献
15.
Bifurcations of nonlinear electron acoustic solitary waves and periodic waves in an unmagnetized quantum plasma with cold and hot electrons and ions has been investigated. The one dimensional quantum hydrodynamic model is used to study electron acoustic waves (EAWs) in quantum plasma. Applying the well known reductive perturbation technique (RPT), we have derived a Korteweg-de Vries (KdV) equation for EAWs in an unmagnetized quantum plasma. By using the bifurcation theory and methods of planar dynamical systems to this KdV equation, we have presented the existence of two types of traveling wave solutions which are solitary wave solutions and periodic traveling wave solutions. Under different parametric conditions, some exact explicit solutions of the above waves are obtained. 相似文献
16.
The nonlinear excitation of fast magnetosonic waves by phase mixing Alfvén waves in a cold plasma with a smooth inhomogeneity of density across a uniform magnetic field is considered. If initially fast waves are absent from the system, then nonlinearity leads to their excitation by transversal gradients in the Alfvén wave. The efficiency of the nonlinear Alfvén–fast magnetosonic wave coupling is strongly increased by the inhomogeneity of the medium. The fast waves, permanently generated by Alfvén wave phase mixing, are refracted from the region with transversal gradients of the Alfvén speed. This nonlinear process suggests a mechanism of indirect plasma heating by phase mixing through the excitation of obliquely propagating fast waves. 相似文献
17.
Impulsively generated waves in solar coronal loops are numerically simulated in the frame-work of cold magnetohydrodynamics. Coronal inhomogeneities are approximated by gas density slabs embedded in a uniform magnetic field. The simulations show that an initially excited pulse results in the propagation of wave packets which correspond to both trapped and leaky waves. Whereas the leaky waves propagate outside the slab, the trapped waves occur as a result of a total reflection from the slab walls. Time signatures of these waves are made by a detection of the trapped waves at a fixed spatial location. For waves excited within the slab, time signatures exhibit periodic, quasi-periodic and decay phases. The time signatures for waves excited outside the slab, or for a multi-series of variously shaped impulses generated at different places and times, can possess extended quasi-periodic phases. The case of parallel slabs, when the presence of a second slab influences the character of wave propagation in the first slab, exhibits complex time signatures as a result of solitary waves interaction. 相似文献
18.
The propagation of MHD waves is studied when two ideal fluids, thermal and suprathermal gases, coupled by magnetic field are
moving with the steady flow velocity. The fluids move independently in a direction perpendicular to the magnetic field but
gets coupled along the field. Due to the presence of flow in suprathermal and thermal fluids there appears forward and backward
waves. All the forward and backward modes propagate in such a way that their rate of change of phase speed with the thermal
Mach number is same. It is also found that besides the usual hydromagnetic modes there appears a suprathermal mode which propagates
with faster speed. Surface waves are also examined on an interface formed with composite plasma (suprathermal and thermal
gases) on one side and the other is a non-magnetized plasma. In this case, the modes obtained are two or three depending on
whether the sound velocity in thermal gas is equal to or greater than the sound velocity in suprathermal gas. The results
lead to the conclusion that the interaction of thermal and suprathermal components may lead to the occurrence of an additional
mode called suprathermal mode whose phase velocity is higher than all the other modes. 相似文献
19.
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
20.
VLF waves in the magnetosphere may be guided by ducts, i.e. enhancements of plasma density aligned with the geomagnetic field. It is required to account for the good transmission properties of these ducts as some leakage of energy is expected, with consequent attenuation. We consider a cylindrical duct, whose axis is parallel to a uniform magnetic field. The electron density of a cold plasma is a function only of radial distance r from the axis, taking constant values in inner and outer regions r < a and r > b, and varying smoothly in the duct wall a < r < b. We compute full-wave ‘trapped’ VLF modes. Results are presented for a range of values of the parameters of the model. In general we find that attenuation of leading modes is very low, agreeing with observation. Specific features are that leakage (arising from mode conversion in the duct wall) increases as the wall is made thinner, that leakage for the leading modes is less for weaker ducts, that many modes may propagate, and that, because of interference effects, some higher order modes also suffer little attenuation. 相似文献