Steady state densities in a plasma confined by a permanent dipole magnet are determined through detailed experiments and modeling. Two diffusion models are developed, and the resulting equations are solved numerically to yield the radial and angular plasma density profiles, which are compared with those obtained experimentally. The models consider the fluid and continuity equations along with Fick’s law and take into account the experimentally determined electron temperature (Te) and the static dipole magnetic fields (B) in space, as a common input. In model I, the equation of motion for both charges (ions and electrons) is used to self-consistently generate the ambipolar electric field (E), while model II considers the electron equation of motion and takes into account the experimentally determined plasma potential (Vs) as another input, whose gradient provides the ambipolar electric field. Results indicate that the plasma density peaks around r ∼ (2–12) cm depending on the polar angle and the discharge pressure and decreases for large r, while its angular variation shows a maximum in the equatorial plane (θ = 90°) and decreases toward the polar regions. Te and Vs are higher in the polar cusp regions and decrease toward the equatorial plane, with the profiles becoming more spherically symmetric away from the magnet. The numerically obtained density profiles from the models agree well with those obtained experimentally. The phenomenon of inward diffusion resulting in peaked density profiles as reported by earlier authors is found to be a natural outcome of the solution of the diffusion equation.

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A generalization of electrical conductivity in a plasma confined in a dipole magnetic field, in the presence of temperature anisotropy is presented. The anisotropy governed by the magnetic field distribution is found to be significant in the strong field region, and has a considerable effect on Pedersen and longitudinal conductivity of electrons over Hall conductivity, whereas the effect of temperature anisotropy on Hall conductivity can be observed in the case of ions. The work reveals new features in the conductivity tensor arising due to the temperature anisotropy and bidirectional nature of the dipole field, by incorporating all possible particle drifts, which would be helpful to enhance the understanding of electrical conduction in both laboratory and space dipole plasmas.

This article presents current density profiles due to Lorentz and hydrodynamic forces in the presence of spatially varying plasma parameters, electrostatic field (E0→), and microwave electric field (E1→̃) obtained from experiments in a plasma confined by a dipole magnet driven at the steady state. The electric field E0→ (or E1→̃) and the pressure tensor P0¯ (or P1¯) were determined to obtain the total current density J0→ (or J1→̃) at various spatial locations employing the electrical conductivity tensor S¯DC (or S¯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 r̂ and θ̂) and grad-curvature drift (along ϕ̂), whereas E→×B→ drift controls the AC density along the three directions, where r̂, θ̂, and ϕ̂ represent unit vectors in spherical polar co-ordinates. The dominance of DC density due to Lorentz and hydrodynamic forces along r̂ and θ̂ directs the particles along the azimuthal direction by J→×B→ 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.