1208.1183 (Anatoly K. Nekrasov)

Back-reaction instabilities of relativistic cosmic rays    [PDF]

Anatoly K. Nekrasov

We explore in the multi-fluid approach streaming instabilities of the electron-ion plasma with relativistic and ultra-relativistic cosmic rays in the background magnetic field. Cosmic rays can be both electrons and protons.The drift speed of cosmic rays is directed along the magnetic field. In equilibrium, the return current of the background plasma is taken into account. One-dimensional perturbations parallel to the magnetic field are considered. The dispersion relations are derived for transverse and longitudinal perturbations. It is shown that the back-reaction of magnetized cosmic rays generates a new instability with the growth rate much larger than that for the Bell instability, while for unmagnetized cosmic rays, the growth rate is analogous to the Bell's. Some difference between two models of the return current in equilibrium is demonstrated. For longitudinal perturbations, an instability is found in the case of ultra-relativistic cosmic rays. The results obtained can be applied for investigations of astrophysical objects such as supernova remnant shocks, galaxy clusters, intracluster medium, and so on.

View original: http://arxiv.org/abs/1208.1183