Electron-acoustic solitons in an electron-beam plasma system

TLDR

Electron‑acoustic solitons are negative electrostatic potential pulses that arise in two‑temperature plasmas, propagate on a few Debye lengths at a velocity between the cold and hot electron thermal speeds, and correspond to localized enhancements of the cold electron density. The study examines the properties of these solitons in detail. Adding an electron beam to the plasma creates new electron‑acoustic solitons whose velocity is linked to the beam speed; below a critical beam velocity these solitons often exhibit positive potential signatures and correspond to cold‑electron density holes, suggesting that recent magnetospheric observations of such holes could reveal these structures.

Abstract

Electron-acoustic solitons exist in a two electron temperature plasma (with “cold” and “hot” electrons) and take the form of negative electrostatic potential pulses. They develop on a spatial scale of a few Debye lengths and propagate at the electron-acoustic velocity which is intermediate between the two electron thermal velocities. They correspond to local enhancement of the cold electron density. It is shown that the introduction of an electron beam in such a plasma allows the existence of new electron-acoustic solitons with velocity related to the beam velocity. Depending on the beam density and temperature and below a critical velocity of the electron beam, they often have a positive potential signature. In such conditions they correspond to electron density holes for the cold electron population. The properties of these solitons are studied in detail. These results suggest that further analysis of recent observations of electron density holes might provide the means to identify these structures in the magnetospheric plasma.