Viscosity of a strongly coupled dust component in a weakly ionized plasma

Effect of Laser Radiation on the Dynamics of Active Brownian Macroparticles in an Extended Plasma-Dust Monolayer

Using the modified method of Brownian dynamics, the dynamics of macroparticles with a uniform metal coating in a plasma-dust monolayer under the action of laser radiation was simulated. The time dependences of the root-mean-square and average linear displacements of particles were calculated for different initial effective parameters of nonideality and different intensities of laser radiation. A relationship was established that connects the effective parameter of nonideality of the dusty plasma system of active particles with the maximum value of the mean linear displacement of particles.

Experiment and model for a Stokes layer in a strongly coupled dusty plasma

A Stokes layer, which is a flow pattern that arises in a viscous fluid adjacent to an oscillatory boundary, was observed in an experiment using a two-dimensional strongly coupled dusty plasma. Liquid conditions were maintained using laser heating, while a separate laser manipulation applied an oscillatory shear that was localized and sinusoidal. The evolution of the resulting flow was analyzed using space-time diagrams. These figures provide an intuitive visualization of a Stokes layer, including features such as the depth of penetration and wavelength. Another feature, the characteristic speed for the penetration of the oscillatory flow, also appears prominently in space-time diagrams. To model the experiment, the Maxwell-fluid model of a Stokes layer was generalized to describe a two-phase liquid. In our experiment, the phases were gas and dust, where the dust cloud was viscoelastic due to strong Coulomb coupling. The model is found to agree with the experiment, in the appearance of the space-time diagrams, and in the values of the characteristic speed, depth of penetration, and wavelength.

Homoclinic chaos in strongly dissipative strongly coupled complex dusty plasmas

The transport properties of the weakly nonlinear (WNL) two-dimensional (2D) quasilongitudinal dust lattice mode is studied in an experimentally realized highly viscous, strongly coupled, weakly ionized plasma [V. E. Fortov et al., Phys. Rev. Lett. 109, 055002 (2012)10.1103/PhysRevLett.109.055002]. The WNL dynamics is found to be described by a 2D dissipative-dispersive nonlinear partial differential equation. The analytical and computational (for gas discharge plasma parameters) results predict strong viscosity induced Shilnikov homoclinic chaos, which, in turn, can cause a phase transition.

Strange attractors induced by melting in systems with nonreciprocal effective interactions

Newton's third law-the action-reaction symmetry-can be violated for effective interbody forces in open and nonequilibrium systems that are ubiquitous in areas as diverse as complex plasmas, colloidal suspensions, active and living soft matter, and social behavior. While studying monolayer complex plasma (confined charged particles in an ionized gas) with nonreciprocal interactions mediated by plasma flows, in silico we found that an interplay between melting and thermal activation drastically transforms the collective dynamics: the order-disorder transition modifies the system's thermal steady state so that the crystal tends to melt, whereas the fluid tends to freeze, jumping chaotically between the two states. We identified this collective chaotic behavior as strange attractors formed in a monolayer complex plasma and link the strange attractor behavior to the specifics of interparticle interactions.

Overestimation of Viscosity by the Green-Kubo Method in a Dusty Plasma Experiment

The Green-Kubo (GK) method is widely used in simulations of strongly coupled plasmas to obtain the viscosity coefficient. However, the method's applicability, which is often taken for granted, has not been tested experimentally. We report an experimental test using a two-dimensional strongly coupled dusty plasma. We find that the GK viscosity is ≈60% larger than the result of a benchmark hydrodynamic method, obtained in the same experiment with the same conditions except for the presence of shear.

Mobility in a strongly coupled dusty plasma with gas

The mobility of a charged projectile in a strongly coupled dusty plasma is simulated. A net force F, opposed by a combination of collisional scattering and gas friction, causes projectiles to drift at a mobility-limited velocity up. The mobility μp=up/F of the projectile's motion is obtained. Two regimes depending on F are identified. In the high-force regime, μp∝F0.23, and the scattering cross section σs diminishes as up-6/5. Results for σs are compared with those for a weakly coupled plasma and for two-body collisions in a Yukawa potential. The simulation parameters are based on microgravity plasma experiments.

Quantum bound of the shear viscosity of a strongly coupled plasma

String theory methods led to the hypothesis that the ratio of a shear viscosity coefficient to the volume density of entropy of any physical system has a lower bound. Systems with strong coupling have a small viscosity as compared to weakly coupled plasmas in which the viscosity is proportional to the mean free path. Here, we have estimated the fully ionized strongly coupled plasma viscosity based on the dynamic experimental data on electrical conductivity and have shown that the ratio of viscosity to entropy of the strongly coupled plasma is very close to that of the lower bound predicted by the string theory.