Propagation of helicon waves with magnetic boundaries

Propagation of bounded whistlers is analyzed in presence of a radially sheared magnetic field (Bo) where the boundary effects are assumed to be provided purely by sharp magnetic field gradients. The propagation of a plane polarized wave requires the constituent left and right circularly polarized waves with single k value to have different radial extents, a condition which is inaccessible in cases of conventional, conducting or dielectric, physical boundaries. The possibility of achieving such a plane polarized bounded mode is explored in an alternate set up with magnetic field boundaries. The results are correlated with experimental observations in the Large Volume Plasma Device (LVPD) where a transition from a right handed to a left handed polarized helicons wave was detected in addition to the presence of a plane polarized wave. When contribution of a nonuniform B$_{o}$ was taken in to account in finding numerical solutions for the wave magnetic field component B$_{z}$(r)a good agreement was recovered with the measured B$_{z}$(r). The numerically obtained k values were used to find a dispersion relation that provided an improved agreement with the measure dispersion data as compared to the conventional Helicon dispersion relation applicable to physical boundaries.