2010/02/25 by A. Bret, M. E. Dieckmann
Physics and Astronomy · #Dust and Plasma Wave Phenomena #Electron #Exponential function #Instability #Ion #Ionosphere and magnetosphere dynamics #Magnetic confinement fusion research #Mass ratio #Nonlinear system #Plasma #Proton #physics.plasm-ph #physics.space-ph
paper · pdf · doi:10.1063/1.3357336
To appear in Physics of Plasmas
arxiv created 2010/02/25 · openalex publication_date 2010/03/01 · arxiv updated 2015/05/18 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
Particle-in-cell simulations are widely used as a tool to investigate instabilities that develop between a collisionless plasma and beams of charged particles. However, even on contemporary supercomputers, it is not always possible to resolve the ion dynamics in more than one spatial dimension with such simulations. The ion mass is thus reduced below 1836 electron masses, which can affect the plasma dynamics during the initial exponential growth phase of the instability and during the subsequent nonlinear saturation. The goal of this article is to assess how far the electron to ion mass ratio can be increased, without changing qualitatively the physics. It is first demonstrated that there can be no exact similarity law, which balances a change in the mass ratio with that of another plasma parameter, leaving the physics unchanged. Restricting then the analysis to the linear phase, a criterion allowing to define a maximum ratio is explicated in terms of the hierarchy of the linear unstable modes. The criterion is applied to the case of a relativistic electron beam crossing an unmagnetized electron-ion plasma.