Kinetic theory of cosmic rays and gamma rays in supernova remnants .1. Uniform interstellar medium

Kinetic models of particle acceleration in supernova remnants (SNRs) are used to determine the cosmic ray (CR) nucleon and, for the first time, also the associated gamma-ray spectrum during SN shock propagation in a uniform interstellar medium. SNR evolution is followed numerically taking into account the backreaction of accelerated CRs on the overall dynamics. The high energy CRs also produce pi(0)-decay gamma-rays. The model for SNRs includes injection of suprathermal particles at the shock front and heating of the thermal plasma due to the dissipation of Alfven waves in the precursor region. It is shown that the CRs are accelerated with very high efficiency. About 50% of the explosion energy is absorbed by CRs at maximum during the SNR evolution even for relatively low injection rates. The maximum energy achieved by accelerated CR protons is about 10(14) eV for a Bohm-limit diffusion coefficient. The main flux of high energy gamma-rays is produced during the early Sedov phase and decreases thereafter. The results are compared with earlier models based on the hydrodynamic approximation for CR transport and test particle estimates. For a moderate ambient gas density of 0.3 I-I-atoms cm(-3), corresponding to a warm interstellar medium, a magnetic field strength of 5 mu G, and an explosion energy of 10(51) erg, the integral TeV gamma-ray flux from a SNR at a distance of 1 kpc exceeds 10(-11) photons cm(-2)s(-1) at peak luminosity, This is higher than previously estimated peak fluxes by factors of the order of 7, and is primarily due to the large shock compression during the sweep-up phase. Spatially, SNRs without. a central compact object are shell sources also in gamma-rays throughout all their evolutionary phases. Given that such SNRs exist close-by they should be observable in particular with sensitive ground based instruments. (C) 1997 Elsevier Science B.V.