Plasma Potential Formation Due to Localized Radio-Frequency Electric Fields

Abstract

A plasma potential formation is investigated in acollisionless magnetized plasma flow in the presence of localizedradio-frequency electric fields. An extremely large-amplitude electronplasma wave is generated by applying an external rf potential to aring exciter surrounding the plasma column. Steep changes of electrondensity, temperature and potential along the plasma flow are observedin the region around the wave generation, where the waves arelocalized because of enhanced wave damping. The phenomena drasticallychange in accordance with the characteristics of electron-wavepropagation. The local potential hill and subsequent large potentialdrop observed are attributed to the ponderomotive force on electronsand the nonlinear electron acceleration due to enhanced wave damping, respectively. This claim is supported by calculations based onone-dimensional Poisson's equation including spatial variations of thecharged particles' velocity distribution functions which are stronglyaffected by the localized highly-nonlinear waves.