Anomalous width variations for ion acoustic rarefactive solitary waves in a warm ion plasma with two electron temperatures

Anomalous width–amplitude variations were observed in large amplitude rarefactive solitary waves which show increasing width with increasing amplitude, contrasting the usual reciprocal relation between the square of the width and the amplitude, beyond a certain value of the plasma parameters [S. S. Ghosh, K. K. Ghosh, and A. N. Sekar Iyengar, Phys. Plasmas, 3, 3939 (1996)]. For the limiting maximum amplitude, the “increasing width” solitary wave tends to a double layer-like solution. The overall variation was found to depend crucially on the specific parameter space. From a detailed investigation of the above behavior, a plausible physical explanation has been presented for such increases in the width. It is found that the ions’ initial kinetic energies and the cold electron concentration within the perturbed region play a significant role in determining the observed width–amplitude variation. This contradicts the investigation of Sayal, Yadav, and Sharma [Phys. Scr. 47, 576 (1993)].