Reabsorption and pile-up of Langmuir waves generated by a hot electron beam propagating through the solar wind plasma

Abstract

The propagation of a cloud of hot electrons in a plasma and generation of Langmuir waves are investigated using numerical simulation of quasilinear equations. It is shown that for an initially stable hot electron beam instability proceeds as a result of advection and generated Langmuir waves are completely reabsorbed by next arriving slower electrons and reabsorption is maximal near the upper velocity boundary of the plateau at the electron distribution function. However, for unstable injection of the beam a part of waves fails to be reabsorbed and remains at the site of injection. The level and spatial extent of these waves depend on the slope of the initial distribution function. For multi-beam injection the number of regions at the site of injection with high level of waves, depends on the temperature of the beams and their separation in the velocity space.