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.

No abstract