Simulated trajectories of electrons bombarding the mask line, as well as incoming electrons from the surface above at different temperatures in the front view. The number of incident electrons in each panel is 25. The red dash indicates the profile of the mask line. Fig. 2 of the paper by Peng Zhang et al. https://doi.org/10.1002/ctpp.202400118
The Cairns–Tsallis (CT) distribution function is employed to model the quasi-neutral region of a basic bounded-plasma system, such as the one described by Tonks and Langmuir (TL). Electrons are assumed to follow the CT distribution, while ions are generated through electron-impact ionization of cold neutral atoms. Under the plasma approximation, the ion velocity distribution function is derived, and fluid moments are taken to evaluate the ion density, temperature, and polytropic coefficient. The results indicate that the ion polytropic coefficient is strongly dependent on the electron nonextensivity () and nonthermality () parameters inherent to the CT distribution. Specifically, an increase in electron nonextensivity leads to a significant deviation in the polytropic index, emphasizing the role of nonthermal effects in plasma behavior. These findings reduce to the Maxwellian case under specific limits, thus, validating the model. The study highlights the relevance of the CT distribution in capturing a broader range of physical phenomena in bounded plasmas, potentially applicable to space and astrophysical plasma environments.
This study delves into the effects of dust size distribution on the properties of shock waves in a dusty plasma, where electrons follow a nonextensive distribution. Employing the reductive perturbation method, the research explores the influence of dust size distribution, modeled by polynomial and power law distributions, on shock wave characteristics such as amplitude, width, and phase velocity. The results reveal that the phase velocity and width of a shock wave considering the dust size distribution are larger than those of the dusty plasma with the averaged dust size. However, the amplitude of a shock wave considering the dust size distribution is smaller than that of the dusty plasma with the averaged dust size. These findings are pivotal for grasping the behavior of shock waves in diverse astrophysical and space plasma contexts where dust particles present a multitude of sizes.
Linear properties of acoustic modes associated with dust-acoustic waves (DAWs) has been examined in a dusty plasma medium containing inertial negatively charged dust species, non-inertial ions following Maxwellian distribution and non-inertial electrons following non-extensive q-distribution. The dust kinematic viscosity and also the dissipation due to the dust-neutral collision have been taken into consideration. The thermal effect of dust species is also taken into account. The linear dispersion relation (LDR) is derived by adopting the normal mode analysis and the linear properties of DAWs is studied for different plasma contexts. It is shown that the propagation zone for DAWs is significantly influenced by the dust-neutral collision and also by the viscosity of dust species. The implications of our results are discussed elaborately in connection with Saturn's rings, Earth's noctilucent clouds (NLC) and DC discharge plasmas.
In this article, we examine different approaches for calculating low frequency opacities in the warm dense matter regime. The relevance of the average-atom approximation and of different models for calculating opacities, such as the Ziman or Ziman–Evans models is discussed and the results compared to ab initio simulations. We begin by recalling the derivation of the Ziman–Evans resistivity from Kubo's linear response theory, using the local approximation to the solutions of the Lippmann–Schwinger equation. With the help of this approximation, we explicitly introduce an ionic structure factor into the Ziman formula, without resorting to the Born approximation. Both approaches involve the calculation of scattering phase shifts, which we integrate from Calogero equation with an adaptive step numerical scheme based on a Runge–Kutta–Merson solver. We show that if the atomic number is not too large, integrating the phase shifts in this way is more time-efficient than using a classical Numerov-type scheme to solve the radial Schrödinger equation. Various approximations are explored for phase shifts to further improve computation time. For the Born approximation, we show that using Born phase shifts directly in the scattering cross-section gives more accurate results than with the integral formula based on the Fourier transform of the electron-ion potential. We also compare an analytical formula based on a Yukawa fit of the electron-ion potential to a numerical integration. The average-atom results are compared with DFT-based molecular dynamics simulations for aluminum in the dilute regime and for copper, aluminum and gold at solid density and different temperatures.
Under the extreme conditions found in small stars, where electron degeneracy and Coulomb coupling are significant, accurate modeling of Thomson scattering is crucial for determining opacity, a primary quantity for stellar energy transport. We use hypernetted-chain calculations, incorporating quantum pseudopotentials and electron-exchange effects to obtain the electron–electron static structure factor to calculate the Thomson scattering transport cross-section for conditions prevailing in the interior of small stars. These results are compared to those from average-atom simulations and analytical calculations. Our findings support laboratory astrophysics experiments aimed at benchmarking opacity models for stellar interiors, particularly for red dwarf stars, and help to bridge theoretical models with observations.
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