“…The negative potential ESWs have been interpreted in terms of ion solitary waves or solitons (Koskinen et al,904 G. S. Lakhina et al: Study of nonlinear ion-and electron-acoustic waves been commonly interpreted in terms of as Bernstein-GreeneKruskal (BGK) modes (Bernstein et al, 1957;Muschietti et al, 1999;Jovanovic and Shukla, 2000;Chen et al, 2005). Other favorite interpretations for these ESWs are based on the nonlinear evolution of a bump-on-tail instability/electron two stream instability (Omura et al, 1996;Kojima et al, 1997;Goldman et al, 1999), and electron-acoustic solitary waves (Pottelette et al, 1990;Dubouloz et al, 1991Dubouloz et al, , 1993Lakhina, 2001, 2004;Tagare et al, 2004. For a detailed discussion of various models, one can refer to Lakhina et al (2000Lakhina et al ( , 2004.…”