Plasma Potential Formation Due to Localized Radio-Frequency Electric Fields

Abstract

A plasma potential formation is investigated in a collisionless magnetized plasma flow in the presence of localized radio-frequency electric fields. An extremely large-amplitude electron plasma wave is generated by applying an external rf potential to a ring exciter surrounding the plasma column. Steep changes of electron density, temperature and potential along the plasma flow are observed in the region around the wave generation, where the waves are localized because of enhanced wave damping. The phenomena drastically change in accordance with the characteristics of electron-wave propagation. The local potential hill and subsequent large potential drop observed are attributed to the ponderomotive force on electrons and the nonlinear electron acceleration due to enhanced wave damping, respectively. This claim is supported by calculations based on one-dimensional Poisson's equation including spatial variations of the charged particles' velocity distribution functions which are strongly affected by the loc...