Reasons for rotating of dust structure in a highly non-uniform magnetic field

A study of a dust trap in a glow discharge in highly non-uniform magnetic field is carried out. The trap is near the end of the solenoid on the side of the anode part of the discharge; it exists only in the magnetic field and it is resistant to its change. In the trap a volume dust structure is formed and comes into rotation with angular velocity of about 10 rad/s depending on the conditions. The interpretation of the reasons of rotation of the dust structure in the detected dust trap is given. Four physical processes known from literature are considered; numerical estimates are made. A feature of the dust trap being studied is a highly non-uniform magnetic field in which the discharge current channel expands and its radial component appears. Ampere force action due to radial component of current and longitudinal component of magnetic field is taken as the reason of dust structure rotation. The numerical estimate for the average section gives the value from 2.5 to 10 rad/s depending on the assumption of the radial component of the current.