RF induced density depletion due to the Ponderomotive force in presence of strong magnetic fields

Adopting the usual cold plasma dielectric tensor and an expression for the Ponderomotive force in presence of a strong magnetic field, it is demonstrated that a rapidly oscillating electric field gives rise to slow time scale drifts which cause density modifications near antennas. Neglecting the magnetic field when deriving the Ponderomotive force leads to a misinterpretation of the direction in which flows are induced. When a strong magnetic field is present, the poloidal gradients of the electric field (in particular near the antenna end points) are at the origin of radial displacements of the plasma while radial electric field gradients have the potential to trigger density inhomogeneity along the antenna. The RF induced plasma drifts are more prominent at higher power and for more evanescent modes.