Stabilization of Flute Instability by Means of High Frequency Field

Abstract

Flute instability is studied theoretically from the point of view of the non-linear interaction of charged particles with an inhomogeneous high frequency field whose electric field component is parallel to the confining magnetic field. The reciprocal action between the high frequency field and the instability is supposed to occur as a result of the particle motions induced by the field parallel to the wave number vector of the instability wave. The two effects of the field are found out; one is attributed to the electron drifts motivated by a quasi-potential derived from the high frequency field and the other is owing to the induced periodic displacement of ions or electrons. The instability is stabilized by the electron drifts whose velocities are nearly equal to or larger than those of ions driving the instability and moreover may be effectively stabilized by the above additional periodic displacements of ions or electrons oscillating with their cyclotron frequencies. These displacements are excited by the high frequency field whose frequency is resonant to half the ion or electron cyclotron frequency.