Huirong Yan, A. Lazarian, R. Schlickeiser
High-energy gamma ray emission has been detected recently from supernovae
remnants (SNRs) and their surroundings. The existence of molecular clouds near
some of the SNRs suggests that the gamma rays originate predominantly from p-p
interactions with cosmic rays accelerated at a closeby SNR shock wave. Here we
investigate the acceleration of cosmic rays and the gamma ray production in the
cloud self-consistently by taking into account the interactions of the
streaming instability and the background turbulence both at the shock front and
in the ensuing propagation to the clouds. We focus on the later evolution of
SNRs, when the conventional treatment of the streaming instability is valid but
the magnetic field is enhanced due to either Bell's current instability and/or
due to the dynamo generation of magnetic field in the precursor region. We
calculate the time dependence of the maximum energy of the accelerated
particles. This result is then used to determine the diffusive flux of the
runaway particles escaping the shock region, from which we obtain the gamma
spectrum consistent with observations. Finally, we check the self-consistency
of our results by comparing the required level of diffusion with the level of
the streaming instability attainable in the presence of turbulence damping. The
energy range of cosmic rays subject to the streaming instability is able to
produce the observed energy spectrum of gamma rays.
View original:
http://arxiv.org/abs/1111.2410
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