Penetration and screening of perpendicularly launched electromagnetic waves through bounded supercritical plasma confined in multicusp magnetic field

The question of electromagnetic wave penetration and screening by a bounded supercritical (omega p > omega with omega p and omega being the electron-plasma and wave frequencies, respectively) plasma confined in a minimum B multicusp field, for waves launched in the k perpendicular to B-o mode, is addressed through experiments and numerical simulations. The scale length of radial plasma nonuniformity (vertical bar n(e)/(partial derivative n(e)/partial derivative r)vertical bar) and magnetostatic field (B-o) inhomogeneity (vertical bar B-o/(partial derivative B-o/partial derivative r)vertical bar) are much smaller than the free space (lambda(o)) and guided wavelengths (zeta(g)). Contrary to predictions of plane wave dispersion theory and the Clemow-Mullaly-Allis (CMA) diagram, for a bounded plasma a finite propagation occurs through the central plasma regions where alpha(2)(p)=omega(2)(p)/omega(2)>= 1 and beta(2)(c)=omega(2)(ce)/omega(2) << 1(similar to 10(-4)), with omega(ce) being the electron cyclotron frequency. Wave screening, as predicted by the plane wave model, does not remain valid due to phase mixing and superposition of reflected waves from the conducting boundary, leading to the formation of electromagnetic standing wave modes. The waves are found to satisfy a modified upper hybrid resonance (UHR) relation in the minimum B field and are damped at the local electron cyclotron resonance (ECR) location. (C) 2011 American Institute of Physics. [doi:10.1063/1.3551696]