Ion Wave Damping in a Nonuniform Plasma

Abstract

The propagation of ion waves externally excited by a gridded electrode in a nonuniform plasma is experimentally investigated. The nonuniformity of the zeroth order drift velocity of ions plays dominating role rather than that of the density in this plasma. The acceleration of ions along the direction of the propagation of ion waves in the presence of the ambipolar field causes an increase in its phase velocity and also an attenuation of the density perturbation. The attenuation is a attributed partly to the loss of the wave momentum due to nonuniformity and partly to an ionization. These new phenomena are examined quantitatively on the basis of the fluid equations using W.K.B. approximation and a rigorous numerical computation.