Magnetized test ions are subjected to acceleration through a numerically simulated oblique double layer in order to determine whether they emerge with velocity vectors aligned with or oblique to the ambient magnetic field. A criterion for oblique alignment, depending on the double-layer parameters and on the external magnetization, is obtained. When it is applied to observed and theoretical auroral double layers, this criterion predicts that accelerated heavy ions will be substantially less magnetic field aligned than will accelerated hydrogen ions, thus suggesting auroral double layers as a source of high-energy ion conics. Test particle simulations are also used to investigate the perpendicular heating of ions at low altitudes by the electric fields associated with moving auroral arcs. The rapid motion of small-scale structures in the arces is suggested as a source of low-energy conical ion distributions, and the slow drifts of the entire arc forms are inferred to heat ionospheric ions.

The production of ion conics by oblique double layers. [of auroral arcs]

Quantum plasmas are an important topic in astrophysics and high pressure laboratory physics for more than 50 years. In addition, many condensed matter systems, including the electron gas in metals, metallic nanoparticles, or electron-hole systems in semiconductors and heterostructures, exhibit—to some extent—plasmalike behavior. Among the key theoretical approaches that have been applied to these systems are quantum kinetic theory, Green function theory, quantum Monte Carlo, semiclassical and quantum molecular dynamics, and more recently, density functional theory simulations. These activities are in close contact with the experiments and have firmly established themselves in the fields of plasma physics, astrophysics, and condensed matter physics. About two decades ago, a second branch of quantum plasma theory emerged that is based on a quantum fluid description and has attracted a substantial number of researchers. The focus of these studies has been on collective oscillations and linear and nonlinear waves in quantum plasmas. Even though these papers pretend to address the same physical systems as the more traditional papers mentioned above, the former appear to form a rather closed community that is largely isolated from the rest of the field. The quantum hydrodynamics (QHD) results have—with a few exceptions—not found application in astrophysics or in experiments in condensed matter physics. Moreover, these results practically did not have any impact on the former quantum plasma theory community. One reason is the unknown accuracy of the QHD for dense plasmas. In this paper, we present a novel derivation, starting from reduced density operators that clearly point to the deficiencies of QHD, and we outline possible improvements. It is also to be noted that some of the QHD results have attracted negative attention being criticized as unphysical. Examples include the prediction of “novel attractive forces” between protons in an equilibrium quantum plasma, the notion of “spinning quantum plasmas,” or the new field of “quantum dusty plasmas.” In the present article, we discuss the latter system in some detail because it is a particularly disturbing case of formal theoretical investigations that are detached from physical reality despite bold and unproven claims of importance for, e.g., dense astrophysical plasmas or microelectronics. We stress that these deficiencies are not a problem of QHD itself, which is a powerful and efficient method, but rather are due to ignorance of its properties and limitations. We analyze the common flaws of these works and come up with suggestions to improve the situation of QHD applications to quantum plasmas.

Quantum hydrodynamics for plasmas—Quo vadis?

: It is shown that under certain approximations the basic system of equations governing the propagation of ion acoustic waves can be reduced to the Kortweg-deVries equation. (Author)

On the propagation of ion acoustic solitary waves of small amplitude.

Charged (nano)particles confined in electrodynamic traps can evolve into strongly correlated Coulomb systems, which are the subject of current investigation. Exciting physical phenomena associated to Coulomb systems have been reported such as autowave generation, phase transitions, system self-locking at the ends of the linear Paul trap, self-organization in layers, or pattern formation and scaling. The dynamics of ordered structures consisting of highly nonideal similarly charged nanoparticles, with coupling parameter of the order $\Gamma = 10^8$ is investigated. This approach enables us to study the interaction of nanoparticle structures in presence and in absence of the neutralizing plasma background, as well as to investigate various types of phenomena and physical forces these structures experience. Applications of electrodynamic levitation for mass spectrometry, including containment and study of single aerosols and nanoparticles are reviewed, with an emphasis on state of the art experiments and techniques, as well as future trends. Late experimental data suggest that inelastic scattering can be successfully applied to the detection of biological particles such as pollen, bacteria, aerosols, traces of explosives or synthetic polymers. Brownian dynamics is used to characterize charged particle evolution in time and thus identify regions of stable trapping. An analytical model is used to explain the experimental results. Numerical simulations take into account the stochastic forces of random collisions with neutral particles, the viscosity of the gas medium, the regular forces produced by the a.c. trapping voltage, and the gravitational force. We show that microparticle dynamics is characterized by a stochastic Langevin differential equation. Laser plasma acceleration of charged particles is also discussed.

The physics and applications of strongly coupled plasmas levitated in electrodynamic traps

A three-dimensional Thomas-Fermi dense anisotropic magnetized plasma containing Fermi-Dirac distributed electrons and ions in addition with classical negatively charged dust grains is considered to analyse oblique modulational instability (MI) and head-on collisions among dust-acoustic (DA) dark solitons. The Chew{Goldberger{Low (CGL) description is employed to dene the anisotropicdust pressure. Following the multiscale reductive perturbation method, the (3+1)-dimensional nonlinear Schrodinger (NLS) equation has been derived and the MI criterion have been identified. It is found that for larger wavelengths, pressure anisotropy have a strong effect on frequency. In addition to that, (un)stable domains of waves as well as amplitude and width of dust acoustic rogue waves(DARWs) are found to be strongly affected by dust grain density, pressure anisotropy and magnetic field. In the stable regions, two Kortweg-de Vries (KdV) equations, their phase shifts and the analytical trajectories of solitary waves are obtained by applying the extended Poincare-Lighthill-Kuo (PLK) method. Numerical analysis reveals that the phase shifts increases with dust concentrationbut decreases with dust pressure anisotropy. The present results may be applicable in exploring the nonlinear wave dynamics and solitary waves interactions in dense astrophysical plasma especially to white dwarfs, interiors of the neutron stars and magnet stars.

Three-dimensional rogue waves and dust-acoustic dark solitons collisions in degenerate ultra dense magnetoplasma in the presence of dust pressure anisotropy

We experimentally investigate the characteristics of a dynamic wake and of flow separation for a square cylinder with steady suction at its leading-edge corners. The wind tunnel experiments were conducted at a Reynolds number of 5946, and suction slots were manufactured symmetrically at the leading corners of the square cylinder. Steady suction was characterized with a suction momentum coefficient Cμ varying from 0.0227 to 0.3182. A time-resolved particle image velocimetry system was used to evaluate the control of leading-edge suction at different Cμ. Next, the measurements were analyzed by applying a proper orthogonal decomposition (POD) to study the control effectiveness. The POD results suggest that the first four modes of wake vortex shedding are transformed in controlled cases and that periodic Karman vortex shedding is suppressed. The results also show that, even with a very small momentum coefficient, the steady suction at the leading-edge corners stabilizes the cylinder wake. The wake region becomes longer and narrower in comparison with the baseline case. In addition, modifications of separation flow were visualized. At quite small Cμ, flow separation at the leading-edge corners is considerably suppressed. Upon increasing the suction momentum coefficient to 0.1364, flow separation at the leading edges is almost eliminated. Finally, we estimate the effect of drag reduction due to the leading-edge suction. 

Characteristics of forced flow past a square cylinder with steady suction at leading-edge corners

The effects of the dust size distribution in ultracold quantum dusty plasmas are investigated. The amplitude ϕm and width ω of quantum dust acoustic waves are studied with different dust size distributions in the system. The ϕm and ω of the quantum dust acoustic waves are found to increase as the total number density increases. The ϕm and ω are greater for unusual dusty plasmas than for typical dusty plasmas. Moreover, as the Fermi temperature of the dust grains increases, the ϕm of the wave decreases. The ω of quantum dust acoustic waves increases as the speed u0 of the wave increases.

Effects of the dust size distribution in one-dimensional quantum dusty plasma

The overtaking collision between two single and unidirectional dust acoustic waves in
dusty plasmas consisting of Boltzmann electrons and ions, and negative dust grains has
been investigated by PIC simulation method. The well-known physical phenomenon is that the
larger soliton moves faster, approaches the smaller one and after the overtaking collision
both resume their original shape and speed with different phase shifts. The merging
amplitude of two solitons and phase shifts of solitons after collision are given. These
PIC results are compared with the overtaking collision of two-soliton solution (TSS) of
KdV equaiton obtained by Hirota bilinear method. Comparisons between two indicates that if
the amplitude of fast soliton is large enough or the amplitude of slow soliton is small
enough, the simulation results are consistent with the interaction of Hirota results.

Numerical modelling of overtaking collisions of dust acoustic waves in plasmas

One-dimensional (1-D) particle-in-cell simulation is used to study the propagation of dark envelop solitons described by the nonlinear Schrodinger equation (NLSE) in electron-ion plasmas. The rational solution of the NLSE is presented, which is proposed as an effective tool for studying the dark envelope soliton in plasma. It is demonstrated by our numerical simulation that there is dark envelope soliton in electron-ion plasmas. The numerical results are in good agreements with the analytical ones from the NLSE which is obtained from the reductive perturbation method. The limitation of the amplitude of dark envelop solitons in plasma is noticed.

Numerical simulation of dark envelope soliton in plasma

Supersoliton (SS) can be mainly featured in two ways, namely, by focusing on subsidiary maxima on its electric field or by meeting the requirement that the appropriate Sagdeev pseudopotential (SP) has three local extrema between the equilibrium conditions and its amplitude In this paper, by using the SP method, double layers and ion-acoustic SSs are studied in a plasma with Maxwellian cold electrons, nonthermal hot electrons, and fluid ions The existence of the SS regime in parameter space is obtained in a methodical fashion The existence domains for positive solitary waves are also presented It is found that there is no SSs at the acoustic speed

Dong-Ning Gao

Papers

Characteristics of forced flow past a square cylinder with steady suction at leading-edge corners

Effects of the dust size distribution in one-dimensional quantum dusty plasma

Numerical modelling of overtaking collisions of dust acoustic waves in plasmas

Numerical simulation of dark envelope soliton in plasma

Ion-acoustic supersolitons and double layers in plasmas with nonthermal electrons