Basic mechanisms of circulation in complex plasmas

Abstract

Summary form only given as follows. Complex plasmas reveal the ability to create and self-sustain large-scale dynamical structures, such as global rotations. Elementary of cell size excited during active dynamical stages due to caged type of particle motion have also been observed. In the report, we focus our attention on the physical mechanism of particle rotations observed in experiments with complex plasmas, which we have termed a circulation' dynamo. The origin of these different activities is still an open issue. One may group the driving mechanisms for complex plasma circulation into the following five categories. (1) Self-sustained non-potential forces exerted on particles (due to inhomogeneous particle charges and/or dispersion in particle sizes, or because of ion drag). A possible physical explanation suggests that the phenomenon can be considered as consequence of the non-Hamiltonian character of complex plasmas. (2) Convective motion of the background neutral gas. This might be an effective mechanism as particles are frictionally coupled to neutral gas. (3) Convective motion of dust particles themselves. Complex (dusty) plasmas represent an excellent example of fluid with background friction. (4) Nucleation and annihilation of defects and defect clusters. Heating induced plasticity or defect modulated melting result in locally non-zero vorticity. (5) Coupled modes based on local or non-local feedback between plasma and particle clouds induced by Rayleigh-Taylor-like instability, two-stream shear instability and others. All these may result in microparticle circling or conveying behaviour observed often in complex plasma experiments.