Experiments on the propagation of an ion-acoustic soliton into a region of inhomogeneous plasma density are described. It is found that the local amplitude and velocity decrease and the width increases as the soliton propagates into a region of lower density. The results are in good agreement with a model based on the KdV equation and with the recent study of Kuehl and Imen [Phys. Fluids 28, 2375 (1985)].

Experiments on the expansion of a plasma into the wake region behind an object inserted in a flowing plasma are described. The dominant expansion mechanism that fills in the wake is determined to be a self-similar expansion. Accelerated ions with a velocity greater than the local ion-acoustic velocity are detected ahead of the self-similar expansion front. In a plasma with two species, two groups of accelerated ions are detected.

In this paper, a mechanism for the excitation of linear and nonlinear ion-acoustic waves in a double plasma machine is suggested. A compressive ion density perturbation is interpreted in terms of "klystron bunching" and a rarefactive ion density perturbation is interpreted in terms of a self-similar expansion. Experimental results support the theoretical model proposed in this paper.

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This paper extends our study on grid excited ion-acoustic solitons to examine far field radiation characteristics. In particular, for propagation distances greater than any launching grid dimension, the solitons propagate as spherically expanding shells.