The influence of the mass-ratio on the acceleration of particles by
  filamentation instabilities
  Almost all sources of high energy particles and photons are associated with
jet phenomena. Prominent sources of such highly relativistic outflows are
pulsar winds and Active Galactic Nuclei. The current understanding of these
jets assumes diluted plasmas which are best described as kinetic phenomena. In
this kinetic description particle acceleration to ultra-relativistic speeds can
occur in completely unmagnetized and neutral plasmas through insetting effects
of instabilities. Even though the morphology and nature of particle spectra are
understood to a certain extent, the composition of the jets is not known yet.
While Poynting-flux dominated jets are certainly composed of electron-positron
plasmas, the understanding of the governing physics in AGN jets is mostly
unclear. In this article we investigate how the constituting elements of an
electron-positron-proton plasma behave differently under the variation of the
fundamental mass-ratio m_p/m_e. We studied initially unmagnetized
counterstreaming plasmas using fully relativistic three-dimensional
particle-in-cell simulations to investigate the influence of the mass-ratio on
particle acceleration and magnetic field generation in electron-positron-proton
plasmas. We covered a range of mass-ratios m_p/m_e between 1 and 100 with a
particle number composition of n_{p^+}/n_{e^+} of 1 in one stream, only protons
are injected in the other, whereas electrons are present in both to guarantee
charge neutrality in the simulation box. We find that with increasing proton
mass the instability takes longer to develop and for mass-ratios > 20 the
particles seem to be accelerated in two phases which can be accounted to the
individual instabilities of the different species. This means that for high
mass ratios the coupling between electrons/positrons and the heavier protons,
which occurs in low mass-ratios, disappears.
