Effects of an Ambipolar Field on Stability of Flute Modes in a Bumpiless Cylinder

Abstract

The effect of an ambipolar field on the stability of electrostatic flute modes for a bumpy torus has been studied for both the positive and negative ambipolar fields using a relatively simple model of a bumpiless cylinder with an artificial gravity. It has been shown that the flute modes are stabilized effectively by the hot electron ring togehter with the rf electric field. The large m number modes (m denotes the azimuthal mode number) are stabilized by the finite Larmor radius effect and the small m number modes are also stabilized by the reduction of gravitational force due to both the hot electron ring and the rf electric field.