New light on ion acoustic solitary waves in a plasma with two-temperature electrons

Ion acoustic solitary waves in two-temperature electron plasmas have been studied in the past, and negative-potential solitons and double layers found, in addition to positive-potential solitons. Here, further investigations show that positive-potential double layers can form below a critical density ratio, associated with the third derivative of the Sagdeev potential evaluated at the origin for the phase velocity of the linear wave. For density ratios that support positive double layers, solitons are also reported beyond the double layers, depending on the cool-to-hot electron temperature ratio. In addition, when both polarities can be supported, solitary structures can propagate at the acoustic speed, contrary to a KdV prescription