DISSIPATION WAVENUMBERS FOR TURBULENCE IN ELECTRON–POSITRON PLASMAS

Abstract

Many astrophysical systems involve turbulent electron-positron plasmas. Linear kinetic theory of electromagnetic fluctuations in homogeneous, magnetized, collisionless, non-relativistic electron-positron plasmas predicts that two lightly damped modes propagate at relatively long wavelengths: an Alfven-like mode with dispersion and a magnetosonic-like mode with dispersion if β e 1. Here, is the Alfven speed in an electron-positron plasma and ∥ refers to the direction parallel to the background magnetic field B o . The dissipation wavenumber kd is defined as the value of k at which the damping rate equals the rate of energy transfer by the turbulent cascade. Using linear theory and a basic turbulent cascade model, kd is predicted for turbulence at propagation quasi parallel to B o , for quasi-perpendicular magnetosonic-like turbulence, and for quasi-perpendicular Alfven-like turbulence. In the latter case, the model predicts that an increase in the turbulent energy should correspond to an increase in kd . The assumptions and predictions of the model may be tested by particle-in-cell simulations.