Confining boundary conditions for simulation of electron-ion plasma by antisymmetrized wave packet molecular dynamics
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The transport of particles and energy that accompanies the trapping of electrons by a finite amplitude drift wave is calculated. Starting from the drift kinetic equation, it is shown that, in the limit of small collision frequency, the electron entropy source is stationary with respect to variations in the electron distribution function. This variational principal is employed, together with the full Fokker–Planck collision operators, to evaluate the electron transport coefficients and, hence, the flux of particles and energy across the magnetic field. Explicit expressions for the particle and energy flux are obtained in terms of the parameters of the plasma-wave system. These expressions should be used in place of the usual quasi-linear expressions for the particle and energy flux when the autocorrelation time of the wave spectrum is sufficient to permit the trapping of electrons by individual waves. These pseudo-classical transport rates are found to be smaller than the quasi-linear expressions that they replace.
Collision frequency
Energy flux
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This paper presents a fully kinetic particle-in-cell simulation of collisionless mesothermal plasma expansion with a focus on the macroscopic electron properties. The results show that the electron thermal properties are anisotropic and nonuniform. In the beam core region, the electrons are thermalized due to interactions between the trapped electrons and the potential well between the beam exit and the beam front. The electron expansion inside the beam is equilibrium and significant cooling occurs associated with the expansion. Immediately out of the beam boundary, the electrons undergo an isothermal expansion. In the outer expansion region, the electrons transition into a nonequilibrium expansion and again exhibit significant cooling. We find that the commonly used assumption of Boltzmann electron simplification is not valid for modeling electrons in mesothermal plasma expansion. An analysis of the electron temperature and density correlation along each individual ion streamlines suggests that simplified models for electron dynamics may be constructed using multiple polytropic laws in different plume regions.
Electron cooling
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The spherical-shell model and the molecular dynamics (MD) method are used to simulate the interactions of energetic C60 clusters with the high-density plasma targets within the framework of the linearized Vlasov–Poisson theory. While the shell model describes Coulomb explosions of randomly oriented clusters under the assumption of isotropic expansion, the MD simulations capture the role of the wake effect in the interionic forces due to the dynamical polarization of the plasma. We find that the vicinage effects in the cluster self-energy, the Coulomb explosion dynamics, and the stopping power are strongly affected by the variations in the cluster speed and the plasma parameters. For example, Coulomb explosions are found to proceed faster for higher speeds, lower plasma densities, and higher electron temperatures. Both approaches show that the cluster stopping power is strongly enhanced in the early stages of Coulomb explosions due to the vicinage effect, but this enhancement eventually diminishes, after the cluster constituent ions are sufficiently separated. This takes place after a penetration time, which is found to be shorter in the MD simulation than in the shell model, owing to the wake-induced elongation of the cluster structure in the course of Coulomb explosion.
Coulomb explosion
Electric potential energy
Poisson's equation
Stopping power
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Transport of a nonneutral electron plasma across a magnetic field is caused by electron scattering from ambient neutral atoms. A theoretical model of such transport is presented, assuming the plasma is quiescent and the scattering is elastic scattering from infinite mass scattering centers of constant momentum transfer cross section. This model is motivated by recent experiments. A reduced transport equation is obtained by expanding the Boltzmann equation for the electron distribution in inverse powers of the magnetic field. The equation together with Poisson’s equation for the radial electric field, which must exist in a nonneutral column, determine the evolution of the system. When these two equations are properly scaled, they contain only a single parameter: the ratio of initial Debye length to initial column radius. For cases where this parameter is either large or small, analytical solutions, or at least partial solutions, are obtained. For intermediate values of the parameter, numerical solutions are obtained.
Electron scattering
Poisson's equation
Debye
Debye sheath
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The ‘‘hydrodynamic model’’ developed by Haas, Holmes, and Lea has been extended to include all elastic collision processes between the species. The properties of the electron momentum equations are investigated in detail; the solution of these equations revealing a critical point along the source axis at which the electron drift velocity reverses direction.
Momentum (technical analysis)
Point source
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Summary form only given, as follows. A dimensionless stability model that tracks the growth and predation of various wave populations is compared with one-dimensional particle-in-cell (PIC) simulations. The stability model uses rate equations to evaluate the coupling of longitudinal waves created by beam-plasma instabilities in order to estimate beam propagation distances. These wave energies and beam propagation distance estimates are compared with bounded one-dimensional PIC simulations. The onset and saturation of the beam-plasma instabilities are evaluated in the simulations. The simulations enable the stability model to be benchmarked and to explore the temporal evolution of background plasma energy distribution, a capability not presently included in the stability model. The scaleable, dimensionless stability model can be used in laboratory and astrophysical parameter regimes while numerical constraints limit the parameter regimes treatable in the PIC simulations.
Dimensionless quantity
Particle-in-cell
Saturation (graph theory)
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Particle (ecology)
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Ambipolar diffusion
Rydberg atom
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Abstract In this paper, the relaxation properties of a fully ionized, hot, ideal plasma have been studied using the molecular dynamics method. As an example, the classical problem of equalization of the electron and ion temperatures for various mass ratios is considered, the relaxation times for temperatures is determined, and the influence of the number of particles and the type of boundary conditions on the simulation results is studied. The simulation results are compared with the available theoretical results.
Positronium
Dynamics
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Summary form only given. We have studied both theoretically and numerically the effects of the space charge field, plasma wave and inhomogeneity of the background magnetic field on the dynamics of electron in an ion channel. For this purpose, we have used a three dimension one-particle simulation code and fourth-order Runge-Kutta method for investigation these effects. The electron dynamics are treated employing complete three-dimensional Lorentz force equations. The trajectories of electron in the ion channel and electron energy gain is well evaluated. Moreover, the optimal values of characteristic wavelength of inhomogeneous magnetic field and plasma frequency for maximum acceleration of electron in an ion channel are achieved.
Lorentz force
Plasma channel
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