Rotation of a single dust granule (spin) is investigated experimentally in a stratified glow discharge. We employ the technique of measurement of the angular velocity, which is based on coordinate tracing of the light scattered by a hollow transparent particle. The angular velocity measured in the experiment is about 1-2 orders of magnitude higher than observed in previous experiments. We found that the angular velocity depends linearly on the discharge current. The mechanism of rotation of the granule is also described.

The investigation of dust structure formed in glow discharge in an external longitudinal magnetic field with induction up to 400 G applied is presented in this work. The dust structure starts to rotate in the magnetic field. The angular-velocity magnitude is one to two orders larger than one in other discharge types. Its dependence on the magnetic field is nonmonotonic. The rotation direction inverses with an increase of the magnetic induction value up to a certain magnitude B0. In close range of induction around B0 and under certain conditions the rotation of the upper and lower parts of the structure in the opposite direction is observed. Rotation is caused by the ion-drag force. The inversion of rotation direction relates with the change of plasma flows in the area of their formation in stratum with the magnetic field applied. The effect of ion flows was investigated in two additional experiments on the observation of structure rotation onset and on gravity-driven probing of stratum. The angular-velocity unhomogeniety allowed us to investigate shearing and to observe melting of the dust crystal. The correlation functions approach showed the occurrence of structure transformation and its phase transition of the meltinglike type in the magnetic field.

Experimental investigation of the rotation of dust structures in a DC discharge in a longitudinal strong magnetic field up to B = 1 T has been performed for the first time. The main problem is the occurrence of discharge instability in moderate fields B > 0.1 T, which we have been able to solve. The dependence of rotation velocity on B is obtained. In fields B < 0.1 T the results are consistent with previous experiments, including rotation inversion. At B > 0.1 T (with the exception of the instability region), a much slower increase in the rotation velocity with increasing B is observed than at B < 0.1 T. In the region B = 0.3-0.4 T, there was a sharp slowing-down of the rotation, apparently due to the instability of the discharge, and a partial degradation of the dust structure occurred.

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Dusty plasma has been studied in dc glow discharge with standing striation formed in neon. The theoretical method of dust particle charge determination is proposed. This method is based on the calculation of the ion and electron fluxes on the dust particle surface in a spatially periodic field of striation. The electron flux is calculated through the use of non-local electron energy distribution function (EEDF), which is formed by inhomogeneous strata potential. The calculation of dust particle charge using proposed theoretical method are compared with those in which the used EEDF was assumed to be Maxwell EEDF. Under the conditions of standing P-striations at low pressures of neon the numerical calculations and the measurements are performed. An experimental method of dust particle charge determination is applied in the dc discharge condition. Discharge current is modulated at low-frequency in order to determine the dust charge through the relaxation oscillation of a single dust particle. The calculation of the dust particle charge with the help of measured frequency and damping coefficient of the oscillations is made. The dust particle charges obtained by using two independent methods are in good agreement.

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The dust particle size distribution in a volume glow discharge dusty plasma is studied. Polydisperse quartz particles are used as a dust component. It is found that a dusty plasma forms in a glow discharge not only in a dust trap but also near the wall at the bottom of the discharge chamber. Dust objects in the latter region are large: they contain up to 30000 particles. The size of particles levitating in discharge striations is three times larger than that of particles levitating near the wall. The idea of using the glow discharge dusty plasma for particle size fractionation of polydisperse powder is put forward.