Self-organized dusty structures in a complex plasma under microgravity conditions: prospects for experimental and theoretical studies
Prokhorov General Physics Institute of the Russian Academy of Sciences, ul. Vavilova 38, Moscow, 119942, Russian Federation
This paper reviews research aimed at understanding phenomena occurring in a complex plasma under microgravity conditions. Some aspects of the already performed work are considered that have not previously been given sufficient attention but which can potentially be crucial for future work. These aspects include, in particular, the observation of compact dusty structures that are estimated to be capable of confining all components of a dusty plasma in a limited volume of space; experimental evidence for the nonlinear screening of dusty particles; experimental evidence for the excitation of collective electric fields; etc. In theoretical terms, novel collective attraction processes between like-charged dusty particles are discussed and all earlier used schemes of shadowy attraction between dusty particles are reviewed and evaluated together with how they can be used to interpret observations. Dusty structures are considered from the point of view of current self-organization theory. It is emphasized that phase transitions between the states of self-organized systems differ significantly from those in homogeneous states and that the phase diagrams should be constructed in terms of the parameters of a self-organized structure and cannot be constructed in terms of temperature and density or similar parameters of homogeneous structures. Using existing theoretical approaches for modeling self-organized structures in a dusty plasma, the parameter distribution of a structure is recalculated for a more simple model that includes the quasineutrality condition and neglects diffusion. These calculations indicate that under microgravity conditions, any self-organized structure can contain a limited number of dusty particles and is finite in size. The maximum possible number of particles in a structure determines the characteristic inter-grain distance in dusty crystals that can be created under microgravity conditions. Crystallization criteria for the structures are examined and quasispherical chambers proposed for future experiments are discussed.