Modulational instability of electron-acoustic waves: an application to auroral zone plasma

By using the standard reductive perturbation technique, a nonlinear Schrödinger equation is derived to study the modulational instability of finite amplitude electron-acoustic waves in an unmagnetized plasma consisting of cold electron fluid and nonthermal electrons. It is found that the presence of nonthermally distributed electrons modifies the domain of the modulational instability and solitary structures. Possibility of stationary states of the wave packets that can appear as envelope solitons under different conditions is explored. The present investigation is relevant to observation from the Viking satellite in the dayside auroral zone.