Experiment of ion-acoustic solitons as an initial value problem

Temporal development of weakly nonlinear, broad ion-acoustic pulses is studied both experimentally and numerically. Compressive, rarefactive and one-cycle sinusoidal initial pulses are used. Experimentally, a train of peaks with soliton-like structure is observed to evolve regardless of which initial perturbation is applied. A numerical solution of a KdV equation indicates that only a few leading peaks evolving from the purely compressive initial pulse can be identified as solitons. The peaks observed for rarefactive perturbation are not solitons although their shape resembles that of the solitons. These peaks do not attain steady state; the amplitude and propagation velocity vary as they propagate. The velocity is slower than that of the ion-acoustic solitons with the same amplitude.