Electron-acoustic solitary waves beyond the Boltzmann approximation: Fully dynamical hot and cold electron fluids

Nonlinear electron-acoustic solitary waves in a collisionless plasma with cold and hot electron populations are investigated using a fully dynamical two-fluid model. Unlike conventional approaches based on the Boltzmann approximation, both electron species are treated dynamically, allowing finite hot electron inertia to be consistently included. The analysis, based on a Sagdeev pseudo-potential formulation in a stationary wave frame, reveals the existence of a finite range of propagation speeds for solitary waves. The lower threshold is associated with supersonic propagation, while the upper limit arises from the loss of bounded nonlinear solutions. Hot electron inertia is found to significantly modifies this existence domain compared to the Boltzmann case. The results demonstrate that the formation and properties of solitary waves are governed by a balance between inertial and thermal effects, providing a physically consistent description of electron-acoustic structures in multi-temperature plasmas.