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1.
In this paper we use a new approach to derive the system of first-order coupled equations governing the propagation of electromagnetic waves in an inhomogeneous magnetized plasma for normal incidence. In this new approach we employ a step model and use Maxwell's equations indirectly. The method we present here possesses simplicity in mathematical manipulation and gives a clearer physical picture of the mechanism of mode-coupling. The variablesE
i used in the coupled equations are directly related to experimental measurements. Our result is shown to be equivalent to that obtained by Budden and Clemmow (1957). 相似文献
2.
The propagation of nonlinear three-dimensional waves in the form of gaussian beams in pulsars is examined. The defining equations
for the wave motion of a plasma with high particle velocities, high electrical conductivity, high wave frequency, and high
magnetic fields are the standard equations of magnetogas dynamics. Nonlinear, time-dependent equations are derived for relatively
small perturbations of the medium and the orders of magnitude of the parameters of motion such that all the terms in the time-dependent
equation are of the same order are written down. Various directions of the unperturbed magnetic field and of the wave propagation
which may arise during plasma motion in quasars are considered. In a number of cases a closed analytic solution can be constructed
for the propagation of axially symmetric gaussian beams.
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Translated from Astrofizika, Vol. 49, No. 3, pp. 409–417 (August 2006). 相似文献
3.
P. C. W. Fung 《Astrophysics and Space Science》1969,5(4):448-458
In this investigation, the polarization transfer equations in terms of the Stokes parameters are derived for electromagnetic waves propagating in an arbitrary direction in an inhomogeneous magnetized plasma. This system of transfer equations is then solved analytically in the case when the magnetized plasma is homogeneous. For simplicity in presentation, the source term in the equation of transfer has been omitted. Transitting to the special case of quasi-longitudinal propagation, the results obtained here are shown to be in agreement to that derived by Zheleznyakov earlier. 相似文献
4.
Abeer A. Mahmoud 《Astrophysics and Space Science》2018,363(1):18
Some important evolution nonlinear partial differential equations are derived using the reductive perturbation method for unmagnetized collisionless system of five component plasma. This plasma system is a multi-ion contains negatively and positively charged Oxygen ions (heavy ions), positive Hydrogen ions (lighter ions), hot electrons from solar origin and colder electrons from cometary origin. The positive Hydrogen ion and the two types of electrons obey \(q\)-non-extensive distributions. The derived equations have three types of ion acoustic waves, which are soliton waves, shock waves and kink waves. The effects of the non-extensive parameters for the hot electrons, the colder electrons and the Hydrogen ions on the propagation of the envelope waves are studied. The compressive and rarefactive shapes of the three envelope waves appear in this system for the first order of the power of the nonlinearity strength with different values of non-extensive parameters. For the second order, the strength of nonlinearity will increase and the compressive type of the envelope wave only appears. 相似文献
5.
The nonlinear wave structures of ion acoustic waves (IAWs) in an unmagnetized plasma consisting of superthermal electrons and warm ions are studied in bounded nonplanar geometry. Using reductive perturbation technique we have derived cylindrical and spherical Korteweg-de Vries (KdV) equations for IAWs to study the propagation of two-solitons. The presence of superthermally distributed electrons is shown to influence the propagation of two-solitons in nonplanar geometry. 相似文献
6.
A reductive perturbation technique is employed to solve the fluid-Poisson equations in spherical geometry describing a weakly nonlinear electron–acoustic (EA) waves in unmagnetized plasma consisting of stationary ions, cold electrons and kappa distributed hot electrons. It is shown that a variable coefficient Kadomtsev–Petviashvili (KP) equation governs the evolution of scalar potential describing propagation of EA waves. The influence of suprathermality and geometry effects on propagation of EA solitary waves is investigated. We found that when electrons evolve toward their thermodynamic equilibrium, EA solitons are generated with large amplitudes. Also it is shown that EA solitary structures can be significantly modified by transverse perturbations. 相似文献
7.
It is known that stellar winds from late type stars are of mixed thermal and magnetic origin. The stellar wind model presented in this work uses the hydrodynamic equations of mass and momentum conservation and closes the system of equations with a detailed energy equation. Both momentum and energy equations have terms due to the effects of Alfvén waves. A smooth transition between the two regimes for Alfvén wave propagation, the undamped and the damped modes, is achieved by considering the geometrical mean of both wave amplitudes. It will be shown that the initial push on the plasma is provided by the mechanical heating input, and that further out the Alfvén waves take over energetically. 相似文献
8.
K. Murawski 《Solar physics》1992,139(2):279-297
The nonlinear propagation of the Alfvén and magnetosonic waves in the solar corona is investigated in terms of model equations. Due to viscous effects taken into account the propagation of the fast wave itself is governed by Burgers type equations possessing both expansion and compression shock solutions. Numerical simulations show that both parallely and perpendicularly propagating fast waves can steepen into shocks if their amplitudes are in excess of some sizeable fraction of the Alfvén velocity. However, if the magnetic field changes linearly in the perpendicular direction, then formation of perpendicular shocks can be hindered. The Alfvén waves exhibit a tendency to drive both the slow and fast magnetosonic waves whose propagation is described by linearized Boussinesq type equations with ponderomotive terms due to the Alfvén wave. The limits of the slow and fast waves are investigated. 相似文献
9.
In electron-positron plasmas the charge-to-mass ratio is the same for both species. This leads for different waves to the vanishing of certain coefficients in the dispersion laws and nonlinear evolution equations, and also to the decoupling of some of the plasma modes. In particular, there is a low-frequency mode which exists at all angles of propagation with respect to the static magnetic field, corresponding at parallel propagation to a degenerate case of circularly polarized waves, and at perpendicular propagation to part of the extraordinary mode. The nonlinear evolution of this generalizedX-mode is governed by a Korteweg-de Vries equation, valid at all angles of propagation except strictly parallel propagation, for which a different approach had been given already. The nonlinearity is strongest at perpendicular propagation. 相似文献
10.
We investigate the propagation of MHD waves in a magnetised plasma in a weakly stratified atmosphere, representative of hot
coronal loops. In most earlier studies, a time-independent equilibrium was considered. Here we abandon this restriction and
allow the equilibrium to develop as a function of time. In particular, the background plasma is assumed to be cooling due
to thermal conduction. The cooling is assumed to occur on a time scale greater than the characteristic travel times of the
perturbations. We investigate the influence of cooling of the background plasma on the properties of magneto–acoustic waves.
The MHD equations are reduced to a 1D system modelling magneto–acoustic modes propagating along a dynamically cooling coronal
loop. A time-dependent dispersion relation that describes the propagation of the magneto–acoustic waves is derived using the
WKB theory. An analytic solution for the time-dependent amplitude of waves is obtained, and the method of characteristics
is used to find an approximate analytical solution. Numerical calculations of the analytically derived solutions are obtained
to give further insight into the behaviour of the MHD waves in a system with a variable, time-dependent background. The results
show that there is a strong damping of MHD waves and the damping also appears to be independent of the position along the
loop. Studies of MHD wave behaviour in a time-dependent backgrounds seem to be a fundamental and very important next step
in the development of MHD wave theory that is applicable to a wide range of situations in solar physics. 相似文献
11.
The paper considers wave coupling for an arbitrary direction of propagation on the basis of single fluid hydromagnetic equations appropriate for a rarefied plasma. The analysis is used to study the transfer of solar wind momenta into the magnetosphere. It is found that wave refraction is significant only during disturbed conditions for waves travelling with the wind. Enhanced reflection of waves might be important even under quiet conditions in the flanks of the magnetosphere. 相似文献
12.
Using the standard reductive perturbation technique, nonlinear cylindrical and spherical Kadomtsev-Petviashvili (KP) equations are derived for the propagation of ion acoustic solitary waves in an unmagnetized collisionless plasma with nonthermal electrons and warm ions. The influence of nonthermally distributed electrons and the effects caused by the transverse perturbation on cylindrical and spherical ion acoustic waves (IAWs) are investigated. It is observed that the presence of nonthermally distributed electrons has a significant role in the nature of ion acoustic waves. In particular, when the nonthermal distribution parameter ?? takes certain values the usual cylindrical KP equation (CKPE) and spherical KP equation (SKPE) become invalid. One then has to have recourse to the modified CKPE or SKPE. Analytical solutions of both CKPE and SKPE and their modified versions are discussed in the present paper. The present investigation may have relevance in the study of propagation of IAWs in space and laboratory plasmas. 相似文献
13.
The nonlinear propagation of ion-acoustic solitary and shock waves in a dissipative, nonplanar quantum plasma comprised of electrons, positrons, and ions are studied. A modified Korteweg-de Vries Burgers equation is derived in the limit of low frequency and long wavelength by taking into account the kinematic viscosity among the plasma constituents. It is shown that this plasma system supports the propagation of both compressive and rarefactive nonlinear waves. The effects of variation of various plasma parameters on the time evolution of nonplanar solitary waves, the profile of shock waves, and the nonlinear structure induced by the collision of solitary waves are discussed. It is found that these parameters have significant effects on the properties of nonlinear waves in cylindrical and spherical geometries, and these effects for compressive and rarefactive nonlinear waves are obviously different. 相似文献
14.
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
15.
16.
In this paper, analytical MHD studies are made on the propagation of oscillatory waves in a semi-infinite plasma which is exposed to an applied magnetic field. The oscillatory wave is introduced into the plasma environment by temperature perturbation.The phase speeds of the resultant disturbance are discussed in terms Grashof, Prandtl, and Eckert numbers (free-convection parameters), Hall parameter, Alfvén parameter, and frequences. Expansion about small Eckert number is made to solve the very nonlinear coupled partial differential equations for the field variables. The appearance of steady streaming at all times in the first order expansion is mentioned. 相似文献
17.
Propagation of waves in a magnetized dusty plasma are studied for all the range of values of ion-cyclotron frequency, and
having streams of electrons and ions. The dispersion relation is obtained for the waves propagating through the dusty plasma
and analysed for different modes of propagation for relative abundance of dust in the plasma. It is observed that abundance
of dust, streaming motions of electrons and ions have an important influence on the propagation of waves in the dusty plasma
particularly when the phase velocity of the wave is in the low frequency region.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
18.
S. A. Elwakil A. Elgarayhi E. K. El-Shewy Abeer A. Mahmoud M. A. El-Attafi 《Astrophysics and Space Science》2013,343(2):661-666
Effect of nonthermality of ions on the propagation of dust-acoustic waves (DAWs) in unmagnetized plasma having electrons, singly charged ions, hot and cold dust grains have been investigated. The reductive perturbation method is employed to reduce the basic set of fluid equations to the Korteweg-de Vries (KdV) equation. Moreover, the energy of two temperatures charged dusty grains were computed. The present investigation can be of relevance to the electrostatic solitary structures observed in various space plasma environments. 相似文献
19.
This paper is devoted to investigate the cold plasma wave properties. The analysis has been restricted to the neighborhood of the pair production region of the Kerr magnetosphere. The Fourier analyzed general relativistic magnetohydrodynamical equations are dealt under special circumstances and dispersion relations are obtained. We find the x-component of the complex wave vector numerically. The corresponding components of the propagation vector, attenuation vector, phase and group velocities are shown in graphs. The direction and dispersion of waves are investigated. 相似文献
20.
The nonlinear propagation of Alfvén waves on open solar magnetic flux tubes is considered. The flux tubes are taken to be vertical and axisymmetric, and they are initially untwisted. The Alfvén waves are time-dependent axisymmetric twists. Their propagation into the chromosphere and corona is investigated by solving numerically a set of nonlinear time-dependent equations, which couple the Alfvén waves into motions parallel to the initial magnetic field (motion in the third coordinate direction is artificially suppressed). The principal conclusions are: (1) Alfvén waves can steepen into fast shocks in the chromosphere. These shocks can pass through the transition region into the corona, and heat the corona. (2) As the fast shocks pass through the transition region, they produce large-velocity pulses in the direction transverse to B
o. The pulses typically have amplitudes of 60 km s–1 or so and durations of a few tens of seconds. Such features may have been observed, suggesting that the corona is in fact heated by fast shocks. (3) Alfvén waves exhibit a strong tendency to drive upward flows, with many of the properties of spicules. Spicules, and the observed corrugated nature of the transition region, may therefore be by-products of magnetic heating of the corona. (4) It is qualitatively suggested that Alfvén waves may heat the upper chromosphere indirectly by exerting time-dependent forces on the plasma, rather than by directly depositing heat into the plasma. 相似文献