Electron beam-plasma interaction and electron-acoustic solitary waves in a plasma with suprathermal electrons

TL;DR

This study investigates how electron beams and suprathermal electrons influence the properties and existence of electron-acoustic solitary waves in a collisionless plasma, revealing that beams can significantly modify wave structures and their parameter ranges.

Contribution

The paper introduces a comprehensive analysis of electron-acoustic solitary waves considering both suprathermal electrons and electron beams, highlighting their combined effects on wave characteristics.

Findings

Electron beams can significantly alter solitary wave structures.

The existence domain of solitons narrows with increased beam speed and temperature ratio.

Electric potential amplitude decreases with higher beam speed and beam-to-cool electron density ratio.

Abstract

Suprathermal electrons and inertial drifting electrons, so called electron beam, are crucial to the nonlinear dynamics of electrostatic solitary waves observed in several astrophysical plasmas. In this paper, the propagation of electron-acoustic solitary waves is investigated in a collisionless, unmagnetized plasma consisting of cool inertial background electrons, hot suprathermal electrons (modeled by a $\kappa$-type distribution), and stationary ions. The plasma is penetrated by a cool electron beam component. A linear dispersion relation is derived to describe small-amplitude wave structures that shows a weak dependence of the phase speed on the electron beam velocity and density. A (Sagdeev-type) pseudopotential approach is employed to obtain the existence domain of large-amplitude solitary waves, and investigate how their nonlinear structures depend on the kinematic and physical properties of the electron beam and the suprathermality (described by $\kappa$) of the hot electrons. The results indicate that the electron beam can largely alter the electron-acoustic solitary waves, but can only produce negative polarity solitary waves in this model. While the electron beam co-propagates with the solitary waves, the soliton existence domain (Mach number range) becomes narrower (nearly down to nil) with increasing the beam speed and the beam-to-hot electron temperature ratio, and decreasing the beam-to-cool electron density ratio in high suprathermality (low $\kappa$). It is found that the electric potential amplitude largely declines with increasing the beam speed and the beam-to-cool electron density ratio for co-propagating solitary waves, but is slightly decreased by raising the beam-to-hot electron temperature ratio.