We report an explanation for the opposite direction of the rotation of the charged dust particles above and below the Helmholtz coil in an inhomogeneous weak magnetic field in the direct current glow discharge. Experiments with monodispersed melamine-formaldehyde particles were performed in an argon plasma in an inhomogeneous weak magnetic field (with the induction values 4, 12, and 18 mT). The linear and angular velocities of rotational motion of the clusters of dust particles formed in regions with an inhomogeneous weak magnetic field above and below the Helmholtz coil were analyzed. The peculiarity is that the directions of rotation in these areas are opposite, whereas there is no rotational motion in the region of a uniform magnetic field. To explain these observations, the theoretical model that takes into account the magnetic field inhomogeneity and provides good agreement with experimental data is presented.
The article presents the preliminary results of an experimental study of the characteristics of a DC stratified glow discharge plasma in an external magnetic field. Single Langmuir probe and emissive spectrometer are used as diagnostic tools for the estimation of various plasma parameters. The main plasma parameters, such as electron temperature, density and floating potential were determined from the voltage-current (VI) characteristics of the probe in the stratified glow discharge plasmas for different magnetic field values. Increasing the value of the magnetic field leads to an increase in the concentration of plasma particles and a decrease in the temperature of electrons. Also by the optical emission spectroscopic (OES) method it was found that the intensity of spectral lines of the stratified glow discharge increases with an increase value of magnetic field. A simple interpretation was made to explain our results according to the work of Bickerton&Engel [21].
In this work, the dynamic behaviour of micron‐sized dust particles suspended in the glow discharge stratum at low pressure in the crossed magnetic and electric fields was experimentally studied. The observations showed that the dust particles move in the direction opposite to the ExB drift with increasing magnetic field induction. When the magnetic field induction reaches a threshold point (B > 10 mT), the dust particles begin to rotate, forming pair of counter‐rotating vortex in the horizontal plane. It was also found that the shape of the dust structures changes from a disk shape to an ellipsoid shape. The dynamic behaviour of the dust vortices was analysed using the PIV (particle image velocimetry) method. The quantitative explanation of the generation of the co‐vortex rotation observed in the experiment was explained on the basis of the charge gradient of the dust particles, which was orthogonal to the ion drag force.
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