Rotational properties of annulus dusty plasma in a strong magnetic field

TL;DR

This study investigates how strong magnetic fields induce and influence rotational motion in annulus dusty plasma, revealing a transition from thermal to rigid body rotation and the effects of magnetic field strength on angular velocity.

Contribution

It provides new insights into the rotational behavior of dusty plasma under strong magnetic fields, including the linear increase and saturation of angular velocity with magnetic field strength.

Findings

Dust grains rotate anticlockwise with increasing magnetic field.

Angular frequency increases linearly up to a threshold and then saturates.

Higher magnetic fields eventually decrease the angular frequency.

Abstract

The collective dynamics of annulus dusty plasma formed between a co-centric conducting (non-conducting) disk and ring configuration is studied in a strongly magnetized radio-frequency (rf) discharge. A superconducting electromagnet is used to introduce a homogeneous magnetic field to the dusty plasma medium. In absence of the magnetic field, dust grains exhibit thermal motion around their equilibrium position. The dust grains start to rotate in anticlockwise direction with increasing magnetic field (B $>$ 0.02 T), and the constant value of the angular frequency at various strengths of magnetic field confirms the rigid body rotation. The angular frequency of dust grains linearly increases up to a threshold magnetic field (B $>$ 0.6 T) and after that its value remains nearly constant in a certain range of magnetic field. Further increase in magnetic field (B $>$ 1 T) lowers the angular frequency. Low value of angular frequency is expected by reducing the width of annulus dusty plasma or the input rf power. The azimuthal ion drag force due to the magnetic field is assumed to be the energy source which drives the rotational motion. The resultant radial electric field in the presence of magnetic field determines the direction of rotation. The variation of floating (plasma) potential across the annular region at given magnetic field explains the rotational properties of the annulus dusty plasma in the presence of magnetic field.