Motion of plasma-dust structures and gas in a magnetic field

Numerous studies have revealed that the superposition of magnetic field causes plasma-dust structures to rotate in the plane normal to the field. The only explanation for this rotation found in the literature is that the plasma-dust structures are acted upon by the forces of ion entrainment (ion drag forces) from ions moving under the effect of the magnetic field in the azimuthal direction. However, this study demonstrates that the experimentally observed motion of plasma-dust structures cannot be explained by the forces of ion entrainment alone. We show that the observed motion of plasma-dust structures is further affected by their entrainment by gas rotating under the effect of the moment of force IxB, which exists in regions of discharge with nonuniform magnetic field in the vicinity of solenoid end faces, as well as at the narrowing of cross section of the discharge channel. An eddy electric current exists in a discharge with strata in a uniform magnetic field; this current causes the rotation of gas and is associated with the noncollinearity of the gradients of plasma density and temperature. Estimates are provided for the density of this current and for its impact on the rotation of gas in a magnetic field. Recent experimental data by Karasev [Phys. Rev. E 74, 066403 (2003)] are discussed.