Fluid dynamic plasma modeling has recently been extended to include the effects of weak coupling, where electromagnetic fields possess a wavelike nature, and charge separation effects, where quasi-neutrality may be violated. In this paper, we present a particular investigation of the MHD rotor problem to illustrate the successful capturing of both weakly coupled and strongly coupled (MHD) limits using the same numerical scheme.

A spatially and temporally resolved measurement of the synchronization of the naturally occurring dust acoustic wave to an external drive and the relaxation from the driven wave mode back to the naturally occuring wave mode is presented. This measurement provides a time-resolved measurement of the s...

[Phys. Rev. E 90, 043103] Published Wed Oct 15, 2014

The phenomenon of phase transition in a dusty-plasma system (DPS) has attracted some attention in the past. Earlier Farouki and Hamaguchi [J. Chem. Phys. 101, 9876 (1994)] have demonstrated the existence of a liquid to solid transition in DPS where the dust particles interact through a Yukawa potential. However, the question of the existence of a vapor-liquid (VL) transition in such a system remains unanswered and relatively unexplored so far. We have investigated this problem by performing extensive molecular dynamics simulations which show that the VL transition does not have a critical curve in the pressure versus volume diagram for a large range of the Yukawa screening parameter κ and the Coulomb coupling parameter Γ. Thus, the VL phase transition is found to be super-critical, meaning that this transition is continuous in the dusty plasma model given by Farouki and Hamaguchi. We provide an approximate analytic explanation of this finding by means of a simple model calculation.

Crack patterns of drying paste and their statistical properties are investigated through smoothed particle hydrodynamics, which is one method for solving continuum equations in the Lagrangian description. In addition to reproducing a realistic crack pattern, we also find that the average area of a f...

[Phys. Rev. E 90, 042909] Published Fri Oct 10, 2014

Finite systems in confining potentials are known to undergo structural
transitions similar to phase transitions. However, these systems are
inhomogeneous, and their "melting" point may depend on the position in the trap
and vary with the particle number. Focusing on three-dimensional Coulomb
systems in a harmonic trap a rich physics is revealed: in addition to radial
melting we demonstrate the existence of intrashell disordering and inter-shell
angular melting. Our analysis takes advantage of a novel melting criterion that
is based on the two and three-particle distribution functions and the
associated reduced entropies which can be directly measured in complex plasma
experiments.

Simple analytical approximations for the internal energy of the strongly coupled one-component-plasma in two and three dimensions are discussed. As a result, new practical expressions for the internal energy in the fluid phase are proposed. Their accuracy is checked by evaluating the location of the fluid-solid phase transition from the free energy consideration. Possible applications to other related systems are briefly discussed.

Nanodust is produced in an rf-driven push-pull parallel-plate reactor using argon with an acetylene admixture at 5–30 Pa. A scheme for the preparation of nanodust clouds with particle radii up to 400 nm for investigations in magnetized plasmas is proposed. The confinement that keeps the nanodust of different radii inside a moderately magnetized discharge (B ≤ 500 mT) is investigated by a comparison of 2d-Langmuir probe measurements in the dust-free plasma without and with a magnetic field and by the analysis of scattered light of nanodust clouds. It is shown that the dust cloud changes its shape when the dust density changes. This results in a reversed α- γ ′ transition from a dense dust cloud with a central disk-like void to a dilute dust cloud with a toroidal void. When the dust density is further reduced, filaments are observed in the central part of the cloud, which were absent in the high-density phase. It is concluded that the dense nanodust cloud is able to suppress plasma filamentation in magnetized plasmas.

Application of the ion sphere model (ISM), well known in the context of the
one-component-plasma, to estimate thermodynamic properties of model Yukawa
systems is discussed. It is shown that the ISM approximation provides fairly
good estimate of the internal energy of the strongly coupled Yukawa systems, in
both fluid and solid phases. Simple expressions for the excess pressure and
isothermal compressibility are derived, which can be particularly useful in
connection to wave phenomena in strongly coupled dusty plasmas. It is also
shown that in the regime of strong screening a simple consideration of
neighboring particles interactions can be sufficient to obtain quite accurate
estimates of thermodynamic properties of Yukawa systems.

An ion beam propagating through a plasma cylinder having negatively charged dust grains drives a low frequency electrostatic dust acoustic wave (DAW) to instability via Cerenkov interaction. The unstable wave frequencies and the growth rate increase with the relative density of negatively charged dust grains. The growth rate of the unstable mode scales to the one-third power of the beam density. The real part of the frequency of the unstable mode increases with the beam energy and scales to almost one-half power of the beam energy. The phase velocity, frequency, and wavelength results of the unstable mode are in compliance with the experimental observations.

An ion beam propagating through a plasma cylinder having negatively charged dust grains drives a low frequency electrostatic dust acoustic wave (DAW) to instability via Cerenkov interaction. The unstable wave frequencies and the growth rate increase with the relative density of negatively charged dust grains. The growth rate of the unstable mode scales to the one-third power of the beam density. The real part of the frequency of the unstable mode increases with the beam energy and scales to almost one-half power of the beam energy. The phase velocity, frequency, and wavelength results of the unstable mode are in compliance with the experimental observations.