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摘要
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 omega(r) = k(parallel to) (upsilon) over bar (A) and a magnetosonic-like mode with dispersion omega(r) similar or equal to k (upsilon) over bar (A) if beta(e) << 1. Here, (upsilon) over bar (A) is the Alfven speed in an electron-positron plasma and parallel to refers to the direction parallel to the background magnetic field B(o). The dissipation wavenumber k(d) 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, k(d) 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 k(d). The assumptions and predictions of the model may be tested by particle-in-cell simulations.
- 出版日期2009-8-20
