The ‘dipole instability’ in complex plasmas and its role in plasma crystal melting (original) (raw)

Melting of monolayer plasma crystals

Physical Review E, 2003

Melting of a monolayer plasma crystal in a radio-frequency discharge with no particles suspended above or below is studied. The experimental data are compared with results of molecular dynamics simulations and theory. It is shown that the melting is caused by the resonance coupling between the longitudinal and the transverse dust-lattice wave modes, due to the interaction of particles with the plasma wakes.

Direct Observation of Mode-Coupling Instability in Two-Dimensional Plasma Crystals

Physical Review Letters, 2010

Dedicated experiments on melting of 2D plasma crystals were carried out. The melting was always accompanied by spontaneous growth of the particle kinetic energy, suggesting a universal plasma-driven mechanism underlying the process. By measuring three principal dust-lattice (DL) wave modes simultaneously, it is unambiguously demonstrated that the melting occurs due to the resonance coupling between two of the DL modes. The variation of the wave modes with the experimental conditions, including the emergence of the resonant (hybrid) branch, reveals exceptionally good agreement with the theory of mode-coupling instability.

Ion temperature gradient instability in a dusty plasma

Physical Review E, 2004

An analysis of the temperature-gradient-driven ͑ i ͒ instability of drift waves in dusty plasma is presented. Various limits that allow for the coupling of the drift wave with the dynamics of dust grains are discussed. In particular, the cases of tiny (magnetized) and relatively heavy (unmagnetized) grains are studied. It is shown that in both limits the behavior of the i mode is considerably affected by the dust dynamics. The growth rate turns out to be higher in the presence of dust, and the instability threshold is lower, resulting in a more unstable plasma.

Complex plasmas: forces and dynamical behaviour

Plasma Physics and Controlled Fusion, 2008

Some peculiar features of complex (dusty) plasmas are reviewed and discussed. In the plasma sheath, the supersonic ion flow causes charge accumulation in the ion wake, which leads to attractive forces between like-charged dust particles. Ion drag is an important force under microgravity conditions, where it produces dust-free regions (voids). It is shown that the same mechanism determines dust confinement in anodic plasmas and leads to torus-shaped dust clouds in magnetized plasmas. Spherical plasma crystals are an interesting object of study which have led to an understanding of the influence of shielding on the structure of trapped particle clouds.

Observations of a structure-forming instability in a dc-glow-discharge dusty plasma

Physical Review E, 2011

By adjusting the anode current and axial magnetic strength of a dc glow discharge dusty plasma, we have found plasma and dust conditions conducive to dusty plasma structurization, similar to one discussed theoretically by Morfill and Tsytovich [Plasma Phys. Reports 26, 682 (2000)]. The structurization instability leads to the formation of a pattern where the dust suspension transforms into alternating stationary regions of high and low dust densities. We have measured the dependence of the wavelength of the non-propagating dust density structures on neutral pressure and plasma density and discussed the results in terms of the dispersion relation obtained by D'Angelo [Phys. of Plasmas 5, 3155 (1998)] for an ionization/ion-drag instability. The observations are also considered in light of a recent theoretical prediction of Khrapak et al. [Phys. Rev. Lett. 102, 245004 (2009)] that under certain conditions the effects of the polarization force on dust particles can cause dust acoustic waves to stop propagating, resulting in the formation of aperiodic, stationary dust density structures.

The influence of the solid to plasma phase transition on the generation of plasma instabilities

Nature Communications

The study of plasma instabilities is a research topic with fundamental importance since for the majority of plasma applications they are unwanted and there is always the need for their suppression. The initiating physical processes that seed the generation of plasma instabilities are not well understood in all plasma geometries and initial states of matter. For most plasma instability studies, using linear or even nonlinear magnetohydrodynamics (MHD) theory, the most crucial step is to correctly choose the initial perturbations imposed either by a predefined perturbation, usually sinusoidal, or by randomly seed perturbations as initial conditions. Here, we demonstrate that the efficient study of the seeding mechanisms of plasma instabilities requires the incorporation of the intrinsic real physical characteristics of the solid target in an electro-thermo-mechanical multiphysics study. The present proof-ofprinciple study offers a perspective to the understanding of the seeding physical mechanisms in the generation of plasma instabilities.

Dynamic behaviors of dust particles in the plasma–sheath boundary

Physics of Plasmas, 2001

A variety of dynamic behaviors in dusty plasmas is expected under the experimental condition of weak friction with gas molecules. The device ''KAGEROU'' provides such an environment for dynamic collective phenomena. Self-excited dust oscillations in Coulomb crystals have been observed at low values of plasma density and gas pressure. An instability mechanism was identified to be delayed charging in an inhomogeneous equilibrium dust charge in the sheath. The theoretical growth rate was formulated in relation to the destabilization of a transverse dust lattice wave ͑T-DLW͒, which was found to be very sensitive to the presence of a small amount of hot electrons which produces a substantial positive equilibrium charge gradient ٌQ d-eq around the equilibrium position of dust particles in the plasma-sheath boundary. The first experimental observation of a correlated self-excited vertical oscillations in a one-dimensional dust chain indicates a destabilization of T-DLW. The experimental condition is very consistent with the parameter area which predicts numerically an instability of T-DLW.