Reductive perturbation method in magnetized plasma and role of negative ions.

An analysis of reductive perturbation method (RPM) is presented to show why the solitary structures of non-linear ion acoustic waves (IAWs) cannot be obtained in magnetized electron ion plasma by employing this technique. In RPM, the non-linear Korteweg–de Vries equation is derived using stretched co-ordinates in the reference frame of the wave phase speed, considering the dispersion to be a higher-order effect that balances the non-linearity to produce a solitary structure. The maximum amplitude | Φ m | of the non-linear solitary wave turns out to be larger than one that contradicts the small amplitude approximation. In the presence of negative ions, the maximum amplitude satisfies the condition | Φ m | < 1. To elaborate these points, the results have been applied to an experimental plasma consisting of positive ions of xenon (Xe +) and negative ions of fluorene (F −) along with electrons. The amplitude and width of the solitary structures depend upon the ratio of the electron to positive ion density ( n e 0 n i 0 ). Since the non-linear coefficient turns out to be negative, rarefied (dip) solitons are formed in the magnetized Xe + − F − − e plasma. [ABSTRACT FROM AUTHOR]