592 research outputs found
Dispersion properties of electrostatic oscillations in quantum plasmas
We present a derivation of the dispersion relation for electrostatic
oscillations (ESOs) in a zero temperature quantum plasma. In the latter,
degenerate electrons are governed by the Wigner equation, while non-degenerate
ions follow the classical fluid equations. The Poisson equation determines the
electrostatic wave potential. We consider parameters ranging from semiconductor
plasmas to metallic plasmas and electron densities of compressed matter such as
in laser-compression schemes and dense astrophysical objects. Due to the wave
diffraction caused by overlapping electron wave function due to the Heisenberg
uncertainty principle in dense plasmas, we have possibility of Landau damping
of the high-frequency electron plasma oscillations (EPOs) at large enough
wavenumbers. The exact dispersion relations for the EPOs are solved numerically
and compared to the ones obtained by using approximate formulas for the
electron susceptibility in the high- and low-frequency cases.Comment: 9 pages, 3 figures. Accepted for publication in Journal of Plasma
Physic
Clustering of ions at atomic dimensions in quantum plasmas
By means of particle simulations of the equations of motion for ions interacting among themselves under the influence of newly discovered Shukla–Eliasson attractive force (SEAF) in a dense quantum plasma, we demonstrate that the SEAF can bring ions closer at atomic dimensions. We present simulation results of the dynamics of an ensemble of ions in the presence of the SEAF without and with confining external potentials and collisions between ions and degenerate electrons. Our particle simulations reveal that under the SEAF, ions attract each other, come closer, and form ionic clusters in the bath of degenerate electrons that shield ions. Furthermore, an external confining potential produces robust ion clusters that can have cigar- and ball-like shapes, which remain stable when the confining potential is removed. The stability of ion clusters is discussed. Our results may have applications to solid density plasmas (density exceeding 1023 per cm3), where the electrons will be degenerate and quantum forces due to the electron recoil effect caused by the overlapping of electron wave functions and electron tunneling through the Bohm potential, electron-exchange and electron-exchange and electron correlations associated with electron-1/2 spin effect, and the quantum statistical pressure of the degenerate electrons play a decisive role
Weibel Instabilities in Dense Quantum Plasmas
The quantum effect on the Weibel instability in an unmagnetized plasma is
presented. Our analysis shows that the quantum effect tends to stabilize the
Weibel instability in the hydrodynamic regime, whereas it produces a new
oscillatory instability in the kinetic regime. A novel effect the quantum
damping, which is associated with the Landau damping, is disclosed. The new
quantum Weibel instability may be responsible for the generation of
non-stationary magnetic fields in compact astrophysical objects as well as in
the forthcoming intense laser-solid density plasma experiments.Comment: Submitted to PR
Strong-coupling effects in the relaxation dynamics of ultracold neutral plasmas
We describe a hybrid molecular dynamics approach for the description of
ultracold neutral plasmas, based on an adiabatic treatment of the electron gas
and a full molecular dynamics simulation of the ions, which allows us to follow
the long-time evolution of the plasma including the effect of the strongly
coupled ion motion. The plasma shows a rather complex relaxation behavior,
connected with temporal as well as spatial oscillations of the ion temperature.
Furthermore, additional laser cooling of the ions during the plasma evolution
drastically modifies the expansion dynamics, so that crystallization of the ion
component can occur in this nonequilibrium system, leading to lattice-like
structures or even long-range order resulting in concentric shells
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