Wen-Shan Duan

Particle-in-cell simulation of the head-on collision between two ion acoustic solitary waves in plasmas

The head-on collision of two ion acoustic solitary waves in plasmas composed of hot electrons and cold ions has been studied by using the Poincare-Lighthill-Kuo (PLK) perturbation method and one-dimensional Particle-in-Cell (PIC) simulation. Then the phase lags of ion acoustic solitary waves (IASWs) obtained from the two approaches have been compared and discussed. It has been found that: if the amplitudes of both the colliding IASWs are small enough, the phase lags obtained from PLK method are in good agreement with those obtained from PIC simulation. As the amplitudes of IASWs increase, the phase lags from PIC simulation become smaller than the analytical ones from PLK method. Besides, the PIC simulation shows the phase lag of an IASW involved in collision depends not only on the characteristics of the wave it collides with but also on itself, which disagrees with the prediction of the PLK method. Finally, the application scopes of the PLK method in studying both the single IASW and the head-on collisio...

Interaction of two solitary waves in quantum electron-positron-ion plasma

The collision between two ion-acoustic solitary waves with arbitrary colliding angle θ in an unmagnetized, ultracold quantum three-component e-p-i plasma has been investigated. By using the extended Poincare-Lighthill-Kuo (PLK) perturbation method, we obtain the KdV equations and the analytical phase shifts after the collision of two solitary waves in this three-component plasma. The effects of the quantum parameter H, the ratio of Fermi positron temperature to Fermi electron temperature σ, the ratio of Fermi positron number density to Fermi electron number density μ, and the ratio of Fermi ion temperature to Fermi electron temperature ρ on the phase shifts are studied. It is found that these parameters can significantly influence the phase shifts of the solitons.

Dust negative ion acoustic shock waves considering dust size distribution effect

A multi-ion dusty plasma containing hot isothermal electrons, ions (light positive ions and heavy negative ions), and extremely and negatively charged dust grains is studied in the present paper. The dust negative ion acoustic shock waves have been investigated by employing the reductive perturbation method. How the dust size distribution affects the height and the thickness of the nonlinear shock wave is studied. It is noted that the different dust size distribution has different shock wave form and different moving speed.

Charge exchange and ionization cross sections of H+ + H collision in dense quantum plasmas

The plasma screening effects of dense quantum plasmas on H+ + H charge exchange and ionization cross sections are calculated by the classical trajectory Monte Carlo method. For charge exchange cross sections, it is found that the screening effects reduce cross sections slightly in weak screening conditions. However, cross sections are reduced substantially in strong screening conditions. For ionization cross sections, with the increase of screening effects, cross sections for low energies increase more rapidly than those for high energies. When the screening effects are strong enough, it is found that ionization cross sections decrease with the increase of incident H+ energy. In addition, the cross sections have been compared with those in weakly coupled plasmas. It is found that in weak screening conditions, plasma screening effects in the two plasmas are approximately the same, while in strong screening conditions, screening effects of dense quantum plasmas are stronger than those of weakly coupled plasmas.

The effect of dust size distribution for the dust acoustic waves in a cold dusty plasma with nonthermal ions

By using the reductive perturbation method, a Kadomtsev–Petviashvili (KP) equation has been derived for the dust acoustic waves (DAW) in an unmagnetized, collisionless and cold dusty plasma with nonthermal ions. It is found that the different dust size distributions have some important effect on the propagating character for dust acoustic solitary waves (DASW) in this system. Meanwhile, it is shown that the velocity of soliton in dusty plasma with power law dust size distribution is larger than that of dusty plasma with mono-sized dust particles. On the other hand, the influence of nonthermal ions on the amplitude and the width of soliton have also been investigated in this paper.

The application scope of the reductive perturbation method and the upper limit of the dust acoustic solitary waves in a dusty plasma

The dust acoustic solitary waves have been numerically investigated by using one dimensional electrostatic particle-in-cell method. By comparing the numerical results with those obtained from the traditional reductive perturbation method, it is found that there exist the maximum dimensionless amplitude and propagation speed of the dust acoustic solitary wave. And these limitations of the solitary wave are explained by using the Sagdeev potential technique. Furthermore, it is noticed that although ϵ ≪ 1 is required in the reductive perturbation method generally, the reductive perturbation method is also valid for ϵu2009<u20091 in a dusty plasma, which may be extended to branches where the reductive perturbation method is used.

The effect of dust size distribution on the damping of the solitary waves in a dusty plasma

The effect of the dust size distribution on the damping rate of the solitary wave in a dusty plasma is investigated in the present paper. It is found that the damping rate increases as either the mean radius of dust grains increases or as the total number density of the dust grains increases. The damping rate is less for usual dusty plasma (about which the number density of the smaller dust grains is larger than that of the larger dust grains) than that of the unusual dusty plasma (about which the number density of the larger dust grains is larger than that of the smaller dust grains).

Dynamics of

Dynamics of He2+ + H ionization in dense quantum plasmas (DQPs) has been studied by the classical trajectory Monte Carlo method. The interactions between charged particles have been described by the exponential cosine-screened Coulomb potential. It is found that ionization cross sections in plasma environments are obviously larger than those in plasma-free environments due to the screening effects. Cross sections for H+ also have been calculated for comparison. For H+, cross sections increase with the increase of screening effects. However, for He2+, cross sections begin to decrease in strong screening effects at intermediate energies. Furthermore, He2+ impact ionization cross sections in weakly coupled plasmas (WCPs) also have been calculated. The interactions have been described by the static screened Coulomb potential. It is found that when screening effects are weak, cross sections in DQPs and WCPs are approximately the same. As screening effects increase, cross sections in DQPs become larger than those in WCPs at high energies. However, when screening effects are strong enough, cross sections in DQPs become smaller than those in WCPs at low and intermediate energies.

H{{e}^{2+}}+H

The effects of dust size distribution and charging process of dust grains on the complex electric conductivity of dusty plasmas have been investigated in the present paper. Comparisons are made between real dusty plasma in which there are many different dust grain species and the mono-sized dusty plasma (MDP) in which there is only one kind of dust grain whose size is the average dust size. In some cases the complex electric conductivity of real dusty plasma is larger than that of MDP, while in other cases it is smaller than that of MDP, it depends on the dust size distribution function.

ionization with exponential cosine-screened Coulomb potential

Damping solitary wave in dusty plasma is studied by considering the collision effect between dust grains and ions. It can be described by a KdV type equation in which a damping term of φ2 exist. It is found that both the amplitude and propagation velocity of the solitary wave decrease with time exponentially. Our results are compared with another KdV type equation with the damping term of φ. It is noted that the damping rate of the KdV type equation with the damping term of φ2 is larger than that with the term of φ. It is found that the damping rate is proportional to the collision frequency between dust grains and ions.