Vladimir Nosenko, Ph.D.
Leader of the GEC plasma laboratory and Research Scientist
Max Planck Institute for Extraterrestrial Physics'
Experimental potential of complex plasmas
Complex, or dusty plasmas are composed of a weakly ionized gas and small charged particles of solid matter. Complex plasmas are important for several reasons. First, the Universe contains a lot of dusty plasma (in star formation regions, interstellar medium, planetary magnetospheres, in the rings of giant planets or in comets). Second, dust poses technological questions in industrial and thermonuclear plasmas. Third, complex plasmas constitute an excellent model system to study liquids and solids at the “atomistic” level.
In a dusty plasma the interparticle distance can be of the order of 0.1 cm, characteristic frequency of the order 10 s-1, and the speed of sound of the order 1 cm/s. Coupling parameter Γ (measured as the ratio of the interparticle potential energy to their kinetic energy) as high as several thousand can be easily achieved in this plasma. These unique characteristics, plus a very helpful possibility of direct imaging, make dusty plasmas an attractive model system to study diverse phenomena at the most fundamental kinetic level.
I will present recent experiments with complex plasmas performed in the lab and even aboard the International Space Station (ISS), mainly along the following lines:
Linear and nonlinear waves. The new wave modes in complex plasmas that arise due to the presence of dust particles are among the most well-studied phenomena in complex plasmas. However, experimental work is only beginning in such areas as wave mode coupling and nonlinear waves. Kinetic effects can also be studied with complex plasmas.
Atomistic dynamics in liquids. Complex plasmas are especially well suited as model systems to study liquids at the level of individual “atoms”. Experiments were performed to measure shear viscosity, thermal conductivity, and diffusion coefficient of complex plasmas. Interesting questions are the applicability of the Navier-Stokes equation at small scale lengths, temperature dependence of thermal conductivity near melting transition, and the very existence of 2D transport coefficients in the thermodynamic limit.
Dust particles as tracers of plasma flows. One interesting application of dusty plasmas is to “visualize” plasma flows using dust particles as tracers. Ion and neutral gas flows were studied using this technique. A new development is applying a rotating electric field to dusty plasma (analogous to the “rotating wall” technique used in non-neutral plasmas). Recent experiments show that dust particles respond to the electric field that rotates with a frequency higher than the dust plasma frequency but lower than ion plasma frequency. A theory was developed to describe the underlying processes in complex plasma.