Problems of nonextensivity in hadron thermodynamics

Hadron thermodynamics deals with a gas of indistinguishable particles whose mass spectrum is taken to have the formKm ^a e ^bm . A long-standing inconsistency is pointed out, namely the nonextensive nature of the entropy found in some treatments by way of the microcanonical ensemble, which contrasts with the extensive nature found by way of the canonical ensemble. The former result is due to an error. After correction, the two ensembles are found to lead to the same expressions for the thermodynamic quantities ifa –7/2. Some of these expressions are new. Fora<–5/2, the microcanonical approach is used to examine a model in which one particle is appreciably heavier than the rest. However, the resulting entropy is found to be unphysical.     

Effects of axial magnetic field and nonextensivity on small amplitude dust acoustic solitary waves in dusty plasma

The nonlinear propagation of small amplitude dust‐acoustic (DA) solitary waves in magnetized dusty plasma consisting of negatively charged mobile dust fluid, and Boltzmann‐distributed electrons and ions with two distinct temperatures following a q‐nonextensive distribution are investigated. In this article, a number of nonlinear equations, namely, the Korteweg–de‐Vries (K‐dV) equations, have been derived by employing the reductive perturbation technique that is valid for a small but finite amplitude limit. The effects of nonextensivity of ions with two distinct temperatures and dust concentration on the amplitude and width of DA solitary waves are investigated theoretically. It is observed that both the nonextensive and low‐temperatures ions significantly modify the basic properties and polarities of DA solitary waves. It is shown that both positive and negative potential DA solitons occur in this case. The implications of these results to some astrophysical environments and space plasmas (e.g., stellar polytropes, peculiar velocity distributions of galaxies, and collisionless thermal plasma), and laboratory dusty plasma systems are briefly mentioned.     

Effect of electron inertia on the speed and shape of ion-acoustic solitary waves in relativistic plasma

Ion-acoustic solitary waves are investigated in a cold collisionless relativistic plasma. Electron inertia is also considered. The Sagdeevs pseudopotential is determined in terms of u, the ion speed and depends on v, the velocity of the wave. It is found that there exists a critical value of u ₁ ( 0), the value of u at which (u)² = 0, beyond which the solitary waves cease to exist. The critical value also depends on the relativistic parameter u ₀/c when u ₀ is the drift velocity of the ion and c is the speed of light.     

Propagation of ion-acoustic waves in a dusty plasma with non-isothermal electrons

For an unmagnetised collisionless plasma consisting of warm ions, nonisothermal electrons and cold, massive and charged dust grains, the Sagdeev potential equation, considering both ion dynamics and dust dynamics has been derived. It has been observed that the Sagdeev potential V(ϕ) exists only for ϕ > 0 up to an upper limit (ϕ ≃ 1.2). This implies the possibility of existence of compressive solitary wave in the plasma. Exhaustive numerics done for both the large-amplitude and small-amplitude ion-acoustic waves have revealed that various parameters, namely, ion temperature, non-isothermality of electrons, Mach numbers etc. have considerable impact on the amplitude as well as the width of the solitary waves. Dependence of soliton profiles on the ion temperature and the Mach number has also been graphically displayed. Moreover, incorporating dust-charge fluctuation and non-isothermality of electrons, a non-linear equation relating the grain surface potential to the electrostatic potential has been derived. It has been solved numerically and interdependence of the two potentials for various ion temperatures and orders of non-isothermality has been shown graphically.      

Ion-acoustic instability in a two-temperature collisional plasma

It is shown that, if one takes account of the non-stationary nature of the background equilibrium, then ion acoustic waves in a two-temperature, collisional, fully ionized plasma are stable.     

电子温度对霍尔推进器等离子体鞘层特性的影响

采用二维粒子模拟方法研究了霍尔推进器通道中电子温度对等离子体鞘层特性的影响, 讨论了不同电子温度下电子数密度、鞘层电势、电场及二次电子发射系数的变化规律. 结果表明: 当电子温度较低时, 鞘层中电子数密度沿径向方向呈指数下降, 在近壁处达到最小值, 鞘层电势降和电场径向分量变化均较大, 壁面电势维持一稳定值不变, 鞘层稳定性好; 当电子温度较高时, 鞘层区内与鞘层边界处电子数密度基本相等, 而在近壁面窄区域内迅速增加, 壁面处达到最大值, 鞘层电势变化缓慢, 电势降和电场径向分量变化均较小, 壁面电势近似维持等幅振荡, 鞘层稳定性降低; 电子温度对电场轴向分量影响较小; 随电子温度的增大, 壁面二次电子发射系数先增大后减少. 关键词： 霍尔推进器 等离子体鞘层 电子温度 粒子模拟     

Arbitrary amplitude dust-acoustic solitary waves in a dusty plasma with flat-topped ion distribution

The properties of arbitrary amplitude dust-acoustic (DA) solitary waves (SWs) in a dusty plasma containing warm adiabatic dust fluid, isothermal electrons and ions following flat-topped velocity distribution is studied by the pseudo-potential approach. The effects of dust temperature and flat-trapped ions are found to significantly modify the basic features of DA-SWs as well modify the parametric regime for the existence of rarefactive solitary waves. The pseudo-potential for small amplitude limit is also analytically analyzed, and the numerical results are found to agree with analytical results.     

Nonlinear Dust Acoustic Waves in Dissipative Space Dusty Plasmas with Superthermal Electrons and Nonextensive Ions

The nonlinear characteristics of the dust acoustic(DA)waves are studied in a homogeneous,collisionless,unmagnetized,and dissipative dusty plasma composed of negatively charged dusty grains,superthermal electrons,and nonextensive ions.Sagdeev pseudopotential technique has been employed to study the large amplitude DA waves.It(Sagdeev pseudopotential)has an evidence for the existence of compressive and rarefractive solitons.The global features of the phase portrait are investigated to understand the possible types of solutions of the Sagdeev form.On the other hand,the reductive perturbation technique has been used to study small amplitude DA waves and yields the Korteweg-de Vries-Burgers(Kd V-Burgers)equation that exhibits both soliton and shock waves.The behavior of the obtained results of both large and small amplitude is investigated graphically in terms of the plasma parameters like dust kinematic viscosity,superthermal and nonextensive parameters.     

Generation of sheath in magnetized plasma under the impact of slow rotation

In this study, we have tried to investigate the generation of sheath in magnetized plasma rotating with a uniform angular velocity about an axis making an angle with the direction of plasma-acoustic wave propagation. In a marked contrast to the earlier studies, here the simultaneous impact of slow rotation and external magnetic field has been taken into consideration. Previous studies have revealed that the Coriolis force generated from rotation has a tendency to produce an equivalent magnetic field effect as and when the ionized medium rotates. The variations of sheath potential with normalized distance for different values of angles of rotation as well as for different values of Mach number have also been investigated for typical plasma parameters.     

Effect of electron inertia on KP solitons in a relativistic plasma

Propagation characteristics of KP solitons in a plasma with finite temperature ions drifting relativistically are investigated. With relativistically drifting ions the electron inertia is important and therefore the finite electron mass is included in the fluid equations instead of the usual Boltzmann distribution for obtaining the Kadomtsev–Petviashvili (KP) equation. Effect of the electron inertia and finite ion temperature is analyzed on the soliton characteristics.     

Solitary ion-acoustic wave propagation in the presence of electron trapping and background nonextensivity

Solitary ion-acoustic wave propagation in the presence of electron trapping is investigated within the theoretical framework of the Tsallis statistical mechanics. A physically meaningful Schamel-like distribution is outlined. In the small amplitude limit, the nonlinear dispersion relation is derived to analyze the global dependency of the main solitary wave quantities. It is found that for a given amplitude and trapping state, the solitary potential structure speeds up and broadens as the electron nonextensivity strengthens. Our results may be of basic interest for experiments that involve particle trapping. The flexibility provided by the nonextensive q-parameter enables one to obtain a good agreement between theory and experiment.     

The two-temperature plasma model of a fireball. The calculated parameters

The analyzed subject is a model of a fireball on the basis of two-temperature plasma. It is hereby recommended to use the offered criteria of plasma confinement and its balance with the environment - atmosphere. You can also see the numerical fit of calculated parameters of internal energy, life time, and surface tension with the analogous parameters of a typical natural fireball.     

双温度氦等离子体输运性质计算

获得覆盖较宽温度和压力范围内的等离子体输运性质是进行等离子体传热和流动过程数值模拟的必要条件.本文采用Saha方程计算等离子体组分, 采用基于将Chapman-Enskog方法扩展到高阶近似的方法, 计算获得了电子温度(T_e)不等于重粒子温度(T_h)的情形下, 在300 K到40000 K的温度范围内氦等离子体的黏性、热导率和电导率. 研究结果表明压力和热力学非平衡参数(θ =T_e/T_h)对氦等离子体的输运性质有较大的影响. 在局域热力学平衡条件下,计算获得的氦等离子体输运性质和文献报道的数据符合良好.     

Effect of cold electron emission on diffusion plasma parameters and the sheath structure in a double plasma device

It is observed experimentally that by injecting cold electrons in the discharge region of a double plasma device, the plasma parameters and sheath structure can be controlled in the other region, which is devoid of any electrical discharge. The main discharge region is separated from the region under investigation by a grounded mesh grid. Both cold and hot ionizing electrons are emitted from separate sets of filaments in the discharge region. With an increase in the cold electron emission current, the plasma parameters in the discharge region get changed, which in turn alter the plasma parameters in the other region. Two important effects caused by cold electrons in the diffusion region are the increase in the plasma density and decrease in the plasma potential. The increase in the plasma density and decrease in the sheath potential drop therefore cause the contraction of the sheath.     

离子对电磁波传播特性的影响

对等离子体中电磁波传播的平板几何模型进行了修正, 讨论了离子对电磁波在大气压均匀非磁化弱电离等离子体中的反射、吸收和透射等传播特性的影响。数值分析的结果表明: 大气条件下, 离子对电磁波在均匀非磁化弱电离等离子体中传播特性的影响是显著的, 同时给出等离子体对电磁波的最大吸收值和吸收宽带。     

Effect of normalized plasma frequency on electron phase-space orbits in a free-electron laser

Irregular phase-space orbits of the electrons are harmful to the electron-beam transport quality and hence deteriorate the performance of a free-electron laser （FEL）. In previous literature, it was demonstrated that the irregularity of the electron phase-space orbits could be caused in several ways, such as varying the wiggler amplitude and inducing sidebands. Based on a Hamiltonian model with a set of self-consistent differential equations, it is shown in this paper that the electron- beam normalized plasma frequency functions not only couple the electron motion with the FEL wave, which results in the evolution of the FEL wave field and a possible power saturation at a large beam current, but also cause the irregularity of the electron phase-space orbits when the normalized plasma frequency has a sufficiently large value, even if the initial energy of the electron is equal to the synchronous energy or the FEL wave does not reach power saturation.     

An entropy group and its representation in thermodynamics of nonextensive systems

The Abel entropy group and its matrix representation with the general law of nonextensive entropy composition and quadratic nonlinearity are defined. Four types of matrices for the corresponding parametrical entropies are given and geometries for their measures are determined. New two-parameter entropy is introduced, and a distribution is found for equilibrium thermodynamics of nonextensive systems. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 79–86, February, 2009.