Ion Acoustic Solitons in a Plasma: A Review of their Experimental Properties and Related Theories

A review of experiments and theories on ion acoustic solitons is presented. Taking into account quadratic nonlinearity in the fluid equations leads to the Korteweg-de Vries (KdV) equation which predicts the existence of solitons. Experimental confirmation of their existence came with the availability of plasmas with large Te/Ti which allows us to minimize damping. However, the experimental datas on the dependency of Mach number vs. soliton amplitude clearly shows a discrepancy with the prediction of the KdV equation. The recent theories do include the effects of finite ion temperature and those due to the trapped electron population. The inclusion of nonlinearity of order higher than quadratic leads to the notion of dressed solitons the dynamic of which has been studied numerically. A discussion of other nonlinear equations describing ion acoustic waves will also be presented.