PIC simulations of Wave bursts – particle interactions in electron-beam Plasmas*

Electron beams in magnetized plasma can be found almost anywhere in space. For example, in the Sun, electron beams are generated in the lower part of the corona. These beams generate Langmuir waves that (through mode conversion) are responsible for the emission of radio waves with different classifications such as types I-IV. Electron beams can also be generated in shocks, in the vicinity of the Earth such as in the dayside polar cusp of Earth, in the auroral region and also electron beams can be found in the polar caps of pulsars’ magnetospheres. In this presentation, we investigate the nonlinear generation of wave bursts triggered by a warm but energetic electron beam using PIC simulations. It is shown, first, that the linear instability peaks at half the electron plasma frequency, which corresponds to the dominant frequency of the coherent waves. Second, we show that the waves have a subpacket structure (or bursts), that have characteristic amplitude profiles similar to envelope solitons arising from the nonlinear Schrodinger equation. Similar wave bursts have recently been seen in electron-beam experiments performed at the NRL Space Physics Simulation Chamber, which we make direct comparisons to. We also briefly discuss the implications of these results to other space environments and to the current state of the of the latest theories.

* Supported by NRL Base Program.

Distribution Statement A. Approved for public release: distribution unlimited.