Study of a condition for the mode conversion from purely perpendicular electrostatic waves to electromagnetic waves

Abstract

One of the mechanisms for generating electromagnetic plasma waves (Z-mode and LO-mode) is mode conversion from electrostatic waves into electromagnetic waves in inhomogeneous plasma. Herein, we study a condition required for mode conversion of electrostatic waves propagating purely perpendicular to the ambient magnetic field, by numerically solving the full dispersion relation. An approximate model is derived describing the coupling between electrostatic waves (hot plasma Bernstein mode) and Z-mode waves at the upper hybrid frequency. The model is used to study conditions required for mode conversion from electrostatic waves (electrostatic electron cyclotron harmonic waves, including Bernstein mode) into electromagnetic plasma waves (LO-mode). It is shown that for mode conversion to occur in inhomogeneous plasma, the angle between the boundary surface and the magnetic field vector should be within a specific range. The range of the angle depends on the norm of the k vector of waves at the site of mode conversion in the inhomogeneous region. The present study reveals that inhomogeneity alone is not a sufficient condition for mode conversion from electrostatic waves to electromagnetic plasma waves and that the angle between the magnetic field and the density gradient plays an important role in the conversion process.

Intense boundary emission destroys normal radio-frequency plasma sheath

“…Electrostatic waves can be excited by applying RF voltage on matched probe immersed in plasma, to be detected and amplified for measurement 54,55 . Strong electrostatic waves generated in IRP can be transformed to electromagnetic radiation through mode conversion in inhomogeneous plasma 56,57 , which is expected to be implemented in related experiments. Note that transverse field shielding is not exactly the same as the model proposed here.…”