共查询到20条相似文献，搜索用时 31 毫秒
1.
Yasunori Nejoh 《Astrophysics and Space Science》1996,235(2):245-253
The stationary ion-acoustic double layer is investigated in a plasma with an electron beam. The condition of the existence sensitively depends on the parameters such as the electron beam temperature, the ion temperature, the beam density and the effect of the trapped electrons. The properties of the double layer are also depicted. It turns out that the electron beam velocity is relatively small. This investigation predicts new findings of the ion-acoustic double layers in a plasma with an electron beam. 相似文献
2.
Gui-Ping Wu Guang-Li Huang Yu-Hua TangDepartment of Physics Southeast University Nanjing Purple Mountain Observatory Chinese Academy of Sciences Nanjing Department of Astronomy Nanjing University Nanjing 《中国天文和天体物理学报》2005,5(1):99-109
Through solving the single electron equation of motion and the Fokker-Planck equation including the terms of electric field strength and ion-acoustic turbulence, we study the influence of the ion-acoustic wave on the electron acceleration in turbulent reconnecting current sheets. It is shown that the ion-acoustic turbulence which causes plasma heating rather than particle acceleration should be considered. With typical parameter values, the acceleration time scale is around the order of 10^-6 s, the accelerated electrons may have approximately a power-law distribution in the energy range 20 ～100 keV and the spectral index is about 3～10, which is basically consistent with the observed hard X-ray spectra in solar flares. 相似文献
3.
H. Alinejad 《Astrophysics and Space Science》2011,331(2):611-618
The effects of dust charge fluctuations and deviations from isothermality of electrons are incorporated in the study of nonlinear
dust ion-acoustic waves. Deviations from isothermality of electrons are included in this model as a result of nonlinear resonant
interaction of the electrostatic wave potential with electrons during its evolution. The basic properties of stationary structures
are studied by employing the reductive perturbation method, and conditions for the formation of small but finite amplitude
dust ion-acoustic solitary waves in the space dusty plasma situations are clearly explained. It is shown that a more depletion
of the background free electrons owing to the attachment of these electrons to the surface of the dust grains during the charging
process can lead to the formation of solitary waves with smaller amplitude. Furthermore, effects of the dust charge fluctuation
and deviations from isothermality of electrons show a non-uniform behavior for the amplitude of solitary waves in transition
from the Boltzmann electron distribution to a trapped electron one. It is also found that the dust charge fluctuation caused
by trapped as well as free electrons is a source of dissipation, and is responsible for the formation of the dust ion-acoustic
shock waves. 相似文献
4.
C.-V. Meister 《Astronomische Nachrichten》1995,316(5):295-310
A Langevin equation for charged particles in a plasma with electrostatic turbulence is developed from first principles and in consistency with the kinetic theory in polarization approximation. For the case of ion-acoustic and electrostatic lower-hybrid-drift turbulence approximate expressions for the space-time spectral density of the wave energy are given and estimates of the intensities of the stochastic wave forces are made. The application is done for the plasmas of the earth's magnetosphere, the solar wind and solar flares. It seems, that ion-acoustic and electrostatic lower-hybrid-drift waves can contribute to electron chaotization in different regions of the space plasma. 相似文献
5.
6.
H. Alinejad 《Astrophysics and Space Science》2010,325(2):209-215
For an unmagnetized collisionless electron–positron–ion plasma, the effects of trapped and non-thermal electron distributions
are incorporated in the study of arbitrary amplitude ion-acoustic solitary structures. Both highly and weakly analyses are
examined by deriving an energy integral equation involving the Sagdeev potential for the large amplitude limit, and obtaining
the non-linear partial-differential equations for the small but finite amplitude limit. It is shown that there exist ion-acoustic
solitary waves with qualitatively different structures in a way that depend on the population of trapped and non-thermal electrons.
In the presence of trapped electrons, fully non-linear analyses show that plasma can support only arbitrary amplitude compressive
solitary waves. On the other hand, a consideration of the fast or non-thermal electron distribution provides the possibility
of the coexistence of large amplitude compressive and rarefactive solitary waves, whereas both of them are decoupled in the
small amplitude limit. It is found that the effects of such electron distributions and positron concentration change the maximum
values of the Mach number and the amplitude for which solitary waves can exist. Furthermore, the non-thermally distributed
electrons provide a KdV equation in the small amplitude limit, whereas the trapped electrons give rise to a modified KdV equation
which exhibits a stronger non-linearity. 相似文献
7.
In high-speed solar wind, propagating Alfvén waves can be transferred into fast magnetosonic waves. When both the magnetic field strength and Alfvén wave velocity approach zero, fast magnetosonic waves will be transferred into ion-acoustic waves. As the phase velocity of ion-acoustic waves is slightly greater than the thermal velocity of protons, the turbulence energy of ion-acoustic waves can largely be absorbed by protons and can cause the mean temperature of protons to be greater than that of electrons by stochastic turbulence heating of ion-acoustic waves for protons. 相似文献
8.
Weak ion-acoustic (IA) solitary wave propagation is investigated in the presence of electron trapping and background nonextensivity. A physically meaningful distribution is outlined and a Schamel-like equation is derived. The role a background electron nonextensivity may play on the energy carried by the IA soliton is then examined. It is found that nonextensivity may cause a soliton energy depletion. An increase of the amount of electron trapping leads to a net shift towards higher values of the soliton energy. 相似文献
9.
Krzysztof Stasiewicz 《Planetary and Space Science》1984,32(3):379-389
On the basis of quasi-linear theory of ion-acoustic turbulence it is shown that the angular and energy distribution of the electron spectra observed in quasi-static inverted-V structures are natural products of electron heating and runaway processes occuring in a region of current-driven turbulence located at h ≈ 1 Re. The power law population J ∞ E?γ, with γ ≈ 1 observed in the energy range ~ 25–1000 eV, is interpreted as a quasi-stationary distribution of suprathermal electrons interacting resonantly with the ion sound waves. This spectrum is generated in the turbulent region and convectively transported earthward along the magnetic field lines. Field-aligned intense electron fluxes with collimation angle < 10° are explained as due to particles escaping from the turbulent region through the runaway cone—a characteristic feature of velocity-space in ion-acoustic turbulence. A complete, new interpretation of the observed electron spectra is given on the basis of the proposed physical acceleration mechanism along with many other implications of this theory. 相似文献
10.
Weak ion-acoustic solitary waves (IASWs) in unmagnetized plasmas having two-fluid ions and kappa-distributed electrons are considered. The effects of electron suprathermality, warm ion temperature and polarity on the nonlinear properties of these IASWs are analyzed. It is found that our present plasma model may support compressive as well as rarefactive solitary structures. 相似文献
11.
A parametric survey on the propagation characteristics of the dust ion-acoustic (DIA) shock waves showing the effect of nonextesivity with nonextensive electrons in a dissipative dusty plasma system has been carried out using the reductive perturbation technique. We have considered continuity and momentum equations for inertial ions, q-distributed nonextensive electrons, and stationary charged dust grains, to derive the Burgers equation. It has been found that the basic features of DIA shock waves are significantly modified by the effects of electron nonextensivity and ion kinematic viscosity. Depending on the degree of nonextensivity of electrons, the dust ion-acoustic shock structures exhibit compression and rarefaction. The implications of our results would be useful to understand some astrophysical and cosmological scenarios like stellar polytropes, hadronic matter and quark-gluon plasma, protoneutron stars, dark-matter halos, etc., where effects of nonextensivity can play the significant roles. 相似文献
12.
The production mechanisms of backscattered electrons and trapped electrons along auroral field lines are examined. The backscattered electrons are produced not only by electron-neutral collisions, but also by electrostatic turbulence predominantly in the ion-cyclotron and ion-acoustic modes. The trapped electrons can only be produced by electron wave turbulence, most likely in the whistler and upper hybrid modes known as the auroral hiss. 相似文献
13.
A model for ion-acoustic waves in the solar atmosphere is presented. In the limit of strongly magnetized plasma this model leads to the Zakharov-Kuznetsov equation which possesses a flat solitary wave solution. An initial-value problem for this equation is solved numerically to show a transition of the flat solitary waves into spherical solitary waves. The paper suggests further developments of an ion-acoustic wave theory that may improve our knowledge of ion-acoustic waves and lead to the possibility of their being detected in the solar atmosphere. 相似文献
14.
V. Krishan 《Solar physics》1980,68(2):343-350
An energetic proton beam passing through a stationary ionized medium, excites ion-acoustic turbulence. The ion-acoustic instability saturates due to the non-linear indirect wave-particle scattering. The electric field associated with the ion-acoustic waves accelerates the plasma particles. Applicability of the results to cometary tails is discussed. 相似文献
15.
Uday Narayan Ghosh Pankaj Kumar Mandal Prasanta Chatterjee 《Astrophysics and Space Science》2014,349(2):765-771
Cylindrical Zakharov–Kuznestov equation for ion-acoustic waves comprising of ions and electrons featuring non-extensive distribution are derived from the fluid equations through reductive perturbation technique. System of first order ordinary differential equations is obtained from Zakharov–Kuznestov equation through dynamical system approach and ultimately it is solved using numerical method. It is found that the electron to positron ratio parameter and the non-extensive distributed parameter due to electron play crucial role on the solution. 相似文献
16.
Weak dust ion-acoustic (DIA) double- layers (DLs) in a dusty plasma with nonextensive electrons are addressed. A generalized Korteweg-de Vries equation with a cubic nonlinearity is derived. It is shown that under certain conditions, the effect of electron nonextensivity can be quite important. In particular, it may be noted that due to the net negative dust charge and electron nonextensivity, the present dusty plasma model may admit compressive as well as rarefactive weak DIA-DLS. Considering the wide relevance of nonlinear oscillations in space dusty plasmas, our investigation may be taken as a prerequisite for the understanding of the nonlinear structures observed in the ionosphere and the auroral acceleration regions. 相似文献
17.
It is shown that a fast ion-acoustic wave can decay into another ion-acoustic wave and a whistler wave. The results are applied to interpret wave spectra measurements in the foreshock region of the Earth's bowshock. 相似文献
18.
H. Alinejad 《Astrophysics and Space Science》2010,327(1):131-137
A theoretical investigation of the one dimensional dynamics of nonlinear electrostatic dust ion-acoustic (DIA) waves in an
unmagnetized dusty plasma consisting of ion fluid, non-thermal electrons and fluctuating immobile dust particles has been
made by the reductive perturbation technique. The basic features of DIA solitary and shock waves are studied by deriving the
Korteweg-de Vries (KdV) and KdV Burger equations, respectively. It is shown that the special patterns of nonlinear electrostatic
waves are significantly modified by the presence of the non-thermal electron component. In particular, the rarefactive solitary
and shock structures are found with smaller amplitude in comparison to the isothermal case. The transition from DIA solitary
to shock waves is also studied which is related to the contributions of the dispersive and dissipative terms. It is found
that the dust charge fluctuation is a source of dissipation, and is responsible for the formation of the dust ion-acoustic
shock waves. Furthermore, the dissipative effect becomes important and may prevail over that of dispersion as the population
of non-thermal electrons present decreases. The present investigation may be of relevance to electrostatic solitary structures
observed in many space dusty plasma, such as Saturn’s E-ring. 相似文献
19.
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
20.
S. A. El-Tantawy N. A. El-Bedwehy S. Khan S. Ali W. M. Moslem 《Astrophysics and Space Science》2012,342(2):425-432
Arbitrary amplitude ion-acoustic solitary waves propagating in a magnetized plasma composed of positive ions, superthermal electrons and positrons are investigated. For this purpose, the ions are represented by the hydrodynamical fluid equations while the non-Maxwellian electrons and positrons densities are assumed to follow kappa (κ) distribution. The basic equations are reduced to a pseudoenergy-balance equation. Existence conditions for large amplitude solitary waves are presented. The analytical and numerical analysis of the latter show that the ion-acoustic solitary wave can propagate only in the subsonic region in our plasma system and it is significantly influenced by the plasma parameters. The present analysis could be helpful for understanding the nonlinear ion-acoustic solitary waves propagating in interstellar medium and pulsar wind, which contain an excess of superthermal particles. 相似文献