Suprathermal electron tails in a beam-plasma instability

Abstract

This study investigated the suprathermal electron tails produced in a beam-plasma instability, and their scaling with beam and background densities. A periodic one-dimensional electrostatic simulation was used to study the suprathermal tails. Electrons were treated as particles, and ions were treated as a fluid. The simulation showed that ion dynamics are required for the formation of the suprathermal tails, as expected from the theory of the oscillating two-stream instability. The energy of the suprathermal tails is directly proportional to the beam density, and does not depend strongly on the background density. There is a slight decrease in the energy of the suprathermal tails as the background density increases. A novel numerical effect was also found: a three-plasmon interaction caused by the modification of the Langmuir wave dispersion relation when high-order splines are used as particle shape factors.