SUPERNOVA REMNANT DYNAMICS AND PARTICLE-ACCELERATION IN ELLIPTIC GALAXIES

Spherically symmetric numerical models of supernova remnants (SNRs) ev olving from the initial explosion up to their final dispersal within t he interstellar medium (ISM) and exploding into a tenuous and hot plas ma are presented. The parameters of the exploding stars are typical fo r an old stellar population (Type I SNe) and the external medium is ch aracterized by a temperature between 10(6)K and 310(7)K with a corresp onding number density of 3 10(-3) cm(-3) and 10(-4) cm(-3) representat ive for the ISM of elliptical galaxies. The magnetic fields vary betwe en 1 mu G and 5 mu G. These models include the diffusive acceleration of charged particles at shock waves by the first order Fermi mechanism , injection of energetic particles at shock waves as well as dissipati on of Alfven waves. Due to the high temperatures and low densities of the ambient medium, the sound velocity is at all evolutionary stages c omparable to the SNR expansion velocity leading to a number of differe nces compared e.g. to the standard Sedov-phase. It is shown that the a cceleration efficiency of cosmic rays in SNRs is significantly reduced . Due to the importance of energetic particles advected into the shock front for these low Mach numbers, injection of particles plays a mino r role and the amount of the SN-explosion energy transferred into cosm ic rays depends on the external population of energetic particles. For standard parameters the mean cosmic ray energy density within an elli ptical galaxy is determined by their surrounding extragalactic values and in the case of no intergalactic cosmic rays the losses of energeti c particles into the extragalactic space can hardly be compensated by acceleration of cosmic rays in SNRs and hence it is difficult to estab lish an equilibrium situation for a cosmic ray population within an el liptical galaxy.