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1.
Compressive solitons of low and high amplitudes are established in this weakly relativistic and magnetized plasma model. The assigned direction of soliton propagation to the direction of the magnetic field, supplemented by the corresponding ion initial streaming speed (v iξ0) determines the lower limit of the initial electron streaming speed (v eξ0) in its interval of existence to produce solitons for a given value of the speed of light c. Further, lower limit of c specified by the corresponding energy (or temperature) to yield relativistic compressive solitons is also predicated. Interestingly, the increased initial streaming speed of electrons is found to play less effective role in the steepening growth of amplitudes of compressive solitons due to mode one than those corresponding to the mode two. 相似文献
2.
In the two component relativistic plasmas subject to pressure variation of adiabatic electrons and isothermal ions, both compressive and rarefactive KdV solitons are established in a quite different physical plasma model. It is desirable to define c s in a new way to substantiate the validity of the model under relativistic effects. The corresponding mathematical condition is also determined, which is a new report of this kind. It is also interesting to report that the relativistic rarefactive solitons cease to exist below some critical ion initial streaming speed v i0 for a fixed temperature α and electron streaming speed v e0. Besides, higher initial flux v i0 of ions under constant temperature is observed to generate higher speed v i at the passage of time which causes to increase (in relativistic sense) its mass diminishing thereby the growth of soliton amplitudes. 相似文献
3.
R. Das 《Astrophysics and Space Science》2012,341(2):543-549
Existence of both compressive and rarefactive solitons are found to exists in a magnetized plasma model consisting of ions, electrons and positive ion beams using the Korteweg-de Vries (KdV) equation. Both fast and slow modes are found to exist due to the presence of ion temperature in the plasma. Moreover, the amplitude of the soliton decreases with an increase in temperature for Q′ (, beam-ion mass to warm-ion mass ratio) >2 and the amplitude becomes maximum when the wave propagates parallel with the direction of the magnetic field. The investigation further revealed that though both compressive and rarefactive solitons exist for slow mode, only compressive soliton exist for the fast mode. 相似文献
4.
Existence of both subsonic and supersonic compressive solitons of interesting characters is established in this magnetized plasma model with non relativistic ions and relativistic electrons. The small supersonic range for the generation of compressive solitons is shown to confine near the vicinity of the direction of the magnetic field. It is predicted that the relativistic variation of electron’s mass is responsible for the expansion of Sagdeev potential to result increase in soliton’s amplitude and decrease in its width. 相似文献
5.
In the new investigation of dust-ion acoustic (DIA) waves with negative dust charges and weakly relativistic ions and electrons in the plasma, compressive and rarefactive DIA solitons of interesting characters are established through the Korteweg-de Vries (KdV) equation. Eventually, the amplitudes of the compressive DIA solitons are found to be constant at some critical temperature ratio α c (electron to ion temperature ratio) identifying some critical dust charge Z dc . It is predicted, that the reception of dust charges by the plasma particles at the variation of temperature starts functioning to the growth of compressive soliton’s constant stage of amplitude after the state of critical α c . The identification of critical dust charge (Z dc ) which is found to be very great for solitons of constant amplitudes becomes feasible for very small dust to ion density ratio (σ). But it can be achieved, we observe, due to the relativistic increase in ion-density as in mass, which is also a salient feature of this investigation. 相似文献
6.
A finite amplitude linearly polarized electromagnetic wave propagating in a relativistic plasma, is found to generate the longitudinal d.c. as well as the oscillating electric field at the second harmonic. In a plasma consisting of only electrons and positrons, these fields cannot be generated.The evolution of the electromagnetic waves is governed by the non-linear Schrödinger equation which shows that the electromagnetic solitons are always possible in ultra-relativistic plasmas (electron-ion or electron-positron) but in a plasma with relativistic electrons and nonrelativistic ions, these solitons exist only if 1(KT
e/meC2)<(2m
i/15me);m
e andm
i being the electron and ion mass andT
e the electron temperature. Both the d.c. electric field and the solitons provide a nonlinear mechanism for anomalous acceleration of the particles. This model has direct relevance to some plasma processes occurring in pulsars. 相似文献
7.
The electrostatic shocks and solitons are studied in weakly relativistic and collisional electron-positron-ion plasmas occurring
in polar regions of pulsar. The plasma system is composed of relativistically streaming electrons, positrons while ions are
taken to be stationary. Dissipative effects in the system are due to collision phenomena among the constituents of relativistic
plasma. Nonlinear dynamics of the dissipation and dispersion dominated relativistic plasma systems are governed by Korteweg-de
Vries Burger (KdVB) and Korteweg-de Vries (KdV) equations respectively. Numerical results, exploring the effects of plasma
parameters on the profile of nonlinear waves are expedited graphically for illustration. Positron to electron temperature
ratio plays the role of a decisive parameter. It is noticed that compressive shocks and solitons evolve in the system if the
positron to electron temperature ratio is less than a critical value. However, there exists a threshold value of positron
to electron temperature ratio beyond which the system supports the rarefactive shocks and solitons. The results may have importance
in the relativistic plasmas of pulsar magnetosphere. 相似文献
8.
As a possible mechanism for particle acceleration in the impulsive phase of solar flares, a new particle acceleration mechanism in shock waves is proposed; a collisionless fast magnetosonic shock wave can promptly accelerate protons and electrons to relativistic energies, which was found by theory and relativistic particle simulation. The simultaneous acceleration of protons and electrons takes place in a rather strong magnetic field such that
ce
pe
. For a weak magnetic field (
ce
pe
), strong acceleration occurs to protons only. Resonant protons gain relativistic energies within the order of the ion cyclotron period (much less than 1 s for solar plasma parameters). The electron acceleration time is shorter than the ion-cyclotron period. 相似文献
9.
It is well known that the parallel cuts of the parallel and perpendicular electric field in electron phase-space holes (electron
holes) have bipolar and unipolar structures, respectively. Recently, electron holes in the Earth’s plasma sheet have been
observed by THEMIS satellites to have detectable fluctuating magnetic field with regular structures. Du et al. (2011) investigated the evolution of a one-dimensional (1D) electron hole with two-dimensional (2D) electromagnetic particle-in-cell
(PIC) simulations in weakly magnetized plasma (Ω
e
<ω
pe
, where Ω
e
and ω
pe
are the electron gyrofrequency and electron plasma frequency, respectively), which initially exists in the simulation domain.
The electron hole is unstable to the transverse instability and broken into several 2D electron holes. They successfully explained
the observations by THEMIS satellites based on the generated magnetic structures associated with these 2D electron holes.
In this paper, 2D electromagnetic particle-in-cell (PIC) simulations are performed in the x–y plane to investigate the nonlinear evolution of the electron two-stream instability in weakly magnetized plasma, where the
background magnetic field (B0 = B0[(e)\vec] x)(\mathbf{B}_{0} =B_{0}\vec{\mathbf{e}} _{x}) is along the x direction. Several 2D electron holes are formed during the nonlinear evolution, where the parallel cuts of E
x
and E
y
have bipolar and unipolar structures, respectively. Consistent with the results of Du et al. (2011), we found that the current along the z direction is generated by the electric field drift motion of the trapped electrons in the electron holes due to the existence
of E
y
, which produces the fluctuating magnetic field δB
x
and δB
y
in the electron holes. The parallel cuts of δB
x
and δB
y
in the electron holes have unipolar and bipolar structures, respectively. 相似文献
10.
It is usually assumed that the ions of cosmic rays contribute nothing to the observable electromagnetic radiation. However, this is true only when these ions are moving in a vacuum or a quiet (nonturbulent) plasma. In the case of fast ions in a turbulent plasma, there is an effective nonlinear mechanism of radiation which is discussed in this paper. The fast ion (relativistic or nonrelativistic) moving in the plasma creates a polarization cloud around itself which also moves with the particles. The turbulent plasma waves may scatter on the moving electric field of this polarization cloud. In the process of this scattering an electromagnetic wave with frequency (2.7) is generated. Let 1 and k1 be the frequency and wave vector of turbulent plasma waves,V is the velocity of the ion, and is the angle between the wave vector of electromagnetic radiation and the direction of the ion velocity. The method of calculating the probability of the conversion of plasma waves (k1) into electromagnetic waves (k) by scattering on an ion with velocityV is described in detal in Section 2 (Equation (2.14)).The spectral coefficients of spontaneous radiation in the case of scattering of plasma waves on polarization clouds created by fast nonrelativistic ions are given in (3.6) for an ion energy distribution function (3.4) and in (3.8) for more general evaluations. The Equations (3.9)–(3.13) describe the spectral coefficients of spontaneous emission for different modes of plasma turbulence (Langmuir (3.9), electron cyclotron in a weak (3.10) or strong (3.11) magnetic field and ion acoustic (3.12)–(3.13) waves). The coefficients of reabsorption or induced emission are given by Equations (3.14) and (3.16)–(3.19). There is a maser effect in the case of scattering of plasma waves on a stream of ions. The effective temperature of the spontaneous emission is given by Equation (3.15). The spectral coefficients of radiation due to scattering of plasma waves on relativistic ions are calculated in the same manner (Equations (4.14)–(4.15)). The total energy loss due to this radiation is given in Equations (4.23)–(4.25). The coefficients of induced emission are given in (4.26)–(4.28).The results are discussed in Section 5. It is shown that the loss of energy by nonlinear plasma radiation is much smaller than the ionization loss. However, the coefficients of synchrotron radiation of electrons and nonlinear radiation of ions under cosmic conditions may be comparable in the case of a weak magnetic field and fairly low frequencies (5.5)–(5.6). Usually the spectrum of nonlinear plasma radiation is steeper than in the case of synchroton radiation. Equation (5.10) gives the condition for nonlinear radiation to prevail over thermal radiation.Translated by D. F. Smith. 相似文献
11.
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
12.
Bahodir B. Ahmedov 《Astrophysics and Space Science》2011,331(2):565-573
The general-relativistic Ohm’s law for a two-component plasma which includes the gravitomagnetic force terms even in the case
of quasi-neutrality has been derived. The equations that describe the electromagnetic processes in a plasma surrounding a
neutron star are obtained by using the general relativistic form of Maxwell equations in a geometry of slow rotating gravitational
object. In addition to the general-relativistic effect first discussed by Khanna and Camenzind (Astron. Astrophys. 307:665,
1996) we predict a mechanism of the generation of azimuthal current under the general relativistic effect of dragging of inertial
frames on radial current in a plasma around neutron star. The azimuthal current being proportional to the angular velocity
ω of the dragging of inertial frames can give valuable contribution on the evolution of the stellar magnetic field if ω exceeds 2.7×1017(n/σ) s−1 (n is the number density of the charged particles, σ is the conductivity of plasma). Thus in general relativity a rotating neutron star, embedded in plasma, can in principle
generate axial-symmetric magnetic fields even in axisymmetry. However, classical Cowling’s antidynamo theorem, according to
which a stationary axial-symmetric magnetic field can not be sustained against ohmic diffusion, has to be hold in the general-relativistic
case for the typical plasma being responsible for the rotating neutron star. 相似文献
13.
Dust acoustic waves are investigated in plasma system containing dynamic and streaming dust, supertherrmal electrons and ions. Linear and nonlinear studies are carried out and elaborated with the help of parameters taken for Saturn’s F-ring. An energy integral equation is obtained by using the Sagdeev potential approach, and results are displayed by solving it analytically and numerically. The dependence of nonlinear structures on κ values, the ratio of electron to dust equilibrium densities μ ed , Mach number M, and dust streaming speed v d0 have been presented. The streaming speed appears as a destructive partner for the Mach number M in the pseudoenergy equation and hence plays a dominant modifying role in the formation of nonlinear structures. It plays a destructive role for some of the solitons and works as a source, for the emergence of new solitons (region). Formation of double layers are also investigated and shown that the amplitude, width and existence of double layers structures are predominantly affected by the presence of superthermal electrons, ions, and streaming dust beam. 相似文献
14.
Ericsson D. Lopez Elisabete M. de Gouveia Dal Pino 《Astrophysics and Space Science》2008,314(1-3):129-136
We here investigate the dispersion properties of radiation in the SS433 relativistic jets. We assume that the jet is composed
of cold electron-proton plasma immersed in a predominantly parallel magnetic field to the jet axis. We find that for the mildly
relativistic source SS433 (for which 〈ψ〉≃79°), the bulk velocity is too small (v≃0.26c) to produce significant changes in the dispersion properties of the medium. Nonetheless, in the rarefied outer regions of
the jets, where radio emission dominates, even a weak magnetic field has some influence on the dispersion properties and there
appear two different electromagnetic branches that are slightly sensitive to the bulk relativistic motion. In the inner, X-ray
region, the magnetic field is much stronger, but in this region the high electron density preserves the isotropic character
of the local plasma and no branch separation occurs. In the region of the jet where the IR and optical emission dominates,
the cold plasma may be also considered isotropic, i.e., neither the magnetic field nor the bulk velocity is able to affect
the propagation of the radiation. Finally, we find that the Doppler line displacement in SS433 is affected by plasma dispersion
only in a narrow frequency range in the far IR. As a consequence, although the shift (z) modulation due to precession of the SS433 jets is well described by previous work, it has to be corrected by plasma dispersion
effects in the far-IR range. 相似文献
15.
Ion-acoustic solitary waves in a warm, magnetized plasma with electron inertia have been investigated through Sagdeev pseudopotential method. It has been established the existence of both compressive supersonic solitons, and rarefactive subsonic and supersonic solitons within the parametric domains. The effect of the external magnetic field for generation of the supersonic compressive solitons of constant amplitudes appears to be passive after some critical direction of propagation of the wave. However, up to the critical direction of propagation, the magnetic resistance is found to be quite active to drastically reduce the soliton amplitudes. The generation of rarefactive solitons in this warm magnetized plasma is rather more feasible to be supersonic without electron inertia. 相似文献
16.
Propagation of small but finite amplitude ion acoustic solitons and double layers are investigated in electron–positron–ion
plasmas in presence of highly negatively charged impurities or dust. The presence of negatively charged dust particulates
can result in existence of two critical concentrations of ion–electron density ratio α. One of them α
D
decides the existence of double layers, whereas the other one α
R
decides the nature of the solitons and double layers. The system supports both compressive and rarefactive solitons as well
as double layers. The parameter regimes of transitions from compressive to rarefactive solitons and double layers are also
specified. 相似文献
17.
Malay Kumar Ghorui Ganesh Mondal Prasanta Chatterjee 《Astrophysics and Space Science》2013,346(1):191-201
Nonlinear propagation of two dimensional dust-acoustic solitary waves in a magnetized quantum dusty plasma whose constituents are electrons, ions, and negatively charged heavy dust particles are investigated using quantum hydrodynamic model. The Zakharov-Kuznetsov (ZK) equation is derived by using reductive perturbation technique (RPT). The higher order inhomogeneous ZK-type differential equation is obtained for the correction to ZK- soliton. The dynamical equation for dressed soliton is solved by using renormalization method. The effects of obliqueness (l x ) of the wave vector, magnetic field strength (B 0), quantum parameter for ions (H i ), soliton velocity (θ) and Fermi temperature ratio (σ) on amplitudes and widths of the ZK-soliton and as well as of the dressed soliton are investigated. The conditions for the validity of the higher order correction are described. Suitable parameter ranges for the existence of compressive and rarefactive dressed solitons are also discussed. 相似文献
18.
In this paper we have investigated the beat wave excitation of an ion-acoustic wave at the difference frequency of two kinetic
(or shear) Alfvén waves propagating in a magnetized plasma with β<1 (β=8π
n
e0
T
e/B
0
2
, where n
e0 is the unperturbed electron number density, T
e is the electron temperature, and B
0 is the external magnetic field). On account of the interaction between two kinetic Alfvén waves of frequencies ω
1 and ω
2, the ponderomotive force at the difference frequency ω
1−ω
2 leads to the generation of an ion-acoustic wave. Also because of the filamentation of the Alfvén waves, magnetic-field-aligned
density dips are observed. In this paper we propose that the ion-acoustic wave generated by this mechanism may be one of the
possible mechanisms for the heating and acceleration of solar wind particles. 相似文献
19.
S. Masson K.-L. Klein R. Bütikofer E. Flückiger V. Kurt B. Yushkov S. Krucker 《Solar physics》2009,257(2):305-322
The origin of relativistic solar protons during large flare/CME events has not been uniquely identified so far. We perform
a detailed comparative analysis of the time profiles of relativistic protons detected by the worldwide network of neutron
monitors at Earth with electromagnetic signatures of particle acceleration in the solar corona during the large particle event
of 20 January 2005. The intensity – time profile of the relativistic protons derived from the neutron monitor data indicates
two successive peaks. We show that microwave, hard X-ray, and γ-ray emissions display several episodes of particle acceleration within the impulsive flare phase. The first relativistic
protons detected at Earth are accelerated together with relativistic electrons and with protons that produce pion-decay γ rays during the second episode. The second peak in the relativistic proton profile at Earth is accompanied by new signatures
of particle acceleration in the corona within ≈1R
⊙ above the photosphere, revealed by hard X-ray and microwave emissions of low intensity and by the renewed radio emission
of electron beams and of a coronal shock wave. We discuss the observations in terms of different scenarios of particle acceleration
in the corona. 相似文献
20.
Venugopal Chandu E. Savithri Devi R. Jayapal George Samuel S. Antony G. Renuka 《Astrophysics and Space Science》2012,339(1):157-164
Kinetic Alfven waves are important in a wide variety of areas like astrophysical, space and laboratory plasmas. In cometary
environments, waves in the hydromagnetic range of frequencies are excited predominantly by heavy ions. We, therefore, study
the stability of the kinetic Alfven wave in a plasma of hydrogen ions, positively and negatively charged oxygen ions and electrons.
Each species was modeled by drifting ring distributions in the direction parallel to the magnetic field; in the perpendicular
direction the distribution was simulated with a loss cone type distribution obtained through the subtraction of two Maxwellian
distributions with different temperatures. We find that for frequencies w* < wcH +\omega^{*} < \omega_{c\mathrm{H}^{ +}} (ω
∗ and wcH +\omega_{c\mathrm{H}^{ +}} being respectively the Doppler shifted and hydrogen ion gyro-frequencies), the growth rate increases with increasing negatively
charged oxygen ion densities while decreasing with increasing propagation angles, negative ion temperatures and negative ion
mass. 相似文献