Dynamics of fine particles in magnetized plasmas

Abstract

Here are presented experiments on fine particles levitating in low-pressure weakly ionized plasmas under a vertical magnetic field. The magnetic field is useful to provide a vertically long cylindrical column of fine-particle clouds, yielding even string-shaped vertically aligned fine particles, under the double-plasma configuration. Measurements show that fine-particle clouds rotate in the azimuthal direction on the horizontal plane even in such a weak magnetic field that positive ions are slightly magnetized. With an increase of the magnetic field, the rotation speed increases, being followed by subsequent saturation. The rotation speed and direction can be controlled by varying radial plasma potential and/or density profiles. The rotation is induced under the condition that the interparticle distance is small enough for the strong Coulomb coupling among fine particles. A mechanism of the rotation could be explained by effects of ion motions on fine particles, which are modified in the presence of the vertical magnetic field.

Coulomb Clusters in Axial Magnetic Field

“…And for the double-ring clusters (planar-10 to planar-12), the angular velocity of the cluster increases very quickly and then saturates even when magnetic strength increases. This phenomenenon is similar to the saturation under the kG magnetic fields reported in [8]. In [10] the possible explanation of saturation was proposed, below we suggest a new explanation of this fact.…”

“…Such systems have been a topic of theoretical and experimental studies with respect to particle ordering, phase transition, energy spectra etc [1][2][3][4]. But up until now, no experiments had been reported on properties of such clusters in magnetic field, while some papers were concerned with the investigation of the behaviour of large plasma crystal in axial magnetic field [5][6][7][8][9].…”

Streaming Complex Plasmas: Ion Susceptibility for a Partially Ionized Plasma in Parallel Electric and Magnetic Fields

“…By adjusting the magnetic field strength it is possible to create plasma states where only the electrons, electrons and ions, or possibly all three charged particle species including the dust particles are magnetized [4]. Several new phenomena have been observed in experiments with magnetic fields, including a slow rotation of the entire dust cloud [5][6][7][8][9], the spinning of dust particles [10], and complicated flow patterns [11]. In recent experiments with strong magnetic fields on the order of a few Tesla, sufficient to magnetize not only the electrons but the ions as well, filaments appeared in the discharge [12].…”

Dissipative drift instability in dusty plasma

“…The behavior of dust grains in plasma in presence of magnetic field has become an interesting topic for investigation in last few years. Sato et al 15 have performed experiment to study dynamics of dust particles in magnetized plasma. They have applied magnetic field upto several Tesla.…”

“…Diamagnetic drift is (15) where, ion-neutral collision frequency is ν in = n n σ in c i (16) while σ in is the ion-neutral collisional cross-section, and…”