Current density profiles in a compact dipole plasma

This article presents current density profiles due to Lorentz and hydrodynamic forces in the presence of spatially varying plasma parameters, electrostatic field ((E) over right arrow (0)), and microwave electric field (<(<(E)over right arrow>)over tilde>(1)) obtained from experiments in a plasma confined by a dipole magnet driven at the steady state. The electric field (E) over right arrow (0) (or <(<(E)over right arrow>)over tilde>(1)) and the pressure tensor (P-0) over bar (or (P-1) over bar) were determined to obtain the total current density (J) over right arrow (0) (or <(<(J)over right arrow>)over tilde>(1) at various spatial locations employing the electrical conductivity tensor (S) over bar (DC) (or (S) over bar (AC)) as obtained in the previous work [Nanda et al., Phys. Plasmas 29, 062105 (2022)]. The results show that the DC density due to hydrodynamic force dominates over those due to the Lorentz force, and the converse is observed in the case of AC density. Furthermore, the DC flow due to the Lorentz force is regulated by bounce motion (along (r) over cap and (theta) over cap) and grad-curvature drift (along (phi) over cap), whereas (E) over right arrow x (B) over right arrow drift controls the AC density along the three directions, where (r) over cap, (theta) over cap, and (phi) over cap represent unit vectors in spherical polar co-ordinates. The dominance of DC density due to Lorentz and hydrodynamic forces along (r) over cap and (theta) over cap directs the particles along the azimuthal direction by (J) over right arrow x (B) over right arrow force. This prevents the loss of particles along the radial and polar directions, thus helping in overall plasma confinement. The work reveals interesting features of current density profiles, guided by bounce motion, magnetic drifts, and anisotropic pressure tensor, which would be beneficial for understanding current flow in laboratory and space dipole plasmas.

Automated summary

This article presents current density profiles in a plasma confined by a dipole magnet, considering the effects of Lorentz and hydrodynamic forces, spatially varying plasma parameters, electrostatic field, and microwave electric field. It is found that the DC density is dominated by hydrodynamic force, while the AC density is dominated by the Lorentz force. The results also reveal the role of bounce motion, magnetic drifts, and anisotropic pressure tensor in controlling the current flow.