Dust-plasma interaction in microgravity complex plasma experiments

Abstract

Micrometer-sized (micro- or dust) particles immersed in the normal laboratory gasdischarges accumulate very high electric charges on their surfaces. Electrostatic interaction energy of the microparticles in plasmas usually significantly exceeds energy of their chaotic motion. The system of microparticles is, therefore, strongly coupled and may be used as an atomistic model of solids and liquids. However, gravitational force plays an important role for the solid particles of micrometer size. To produce undisturbed 3-dimensional structures, microgravity is required. Under microgravity conditions, the microparticles fill practically the entire plasma volume, in most of the cases significantly affecting the plasma properties. The following physical mechanisms of microparticle (dust) and plasma interaction relevant for microgravity complex plasma experiments will be discussed. Microparticles in lowtemperature plasmas immobilize significant fraction of negative charge, their surface represents a sink of electrons and ions, interplay between the electrostatic and ion drag forces leads to strong inhomogeneities in the dust component. As a consequence, plasma parameters change locally and redistribute globally [1], new types of instabilities (e.g. heartbeat instability [2]) arise. The experiments performed on a laboratory prototype of PK3-plus space experiment and in parabolic flights with PK-4 facility will be presented. References: 1. S. Mitic et al., New J. Phys., 11, 083020, (2009). 2. M. Pustylnik et al., Phys. Plasmas, 19, 103701, (2012).