Validity of PlaneWave Approach for Cosmic Ray Acceleration by Supernova Shocks
Abstract
We describe a direct comparison between a planewave,steadystate approach and a kinetic model for cosmic ray (CR) acceleration by an expanding, spherical shock. We show that the planewave approximation adequately describes the nonlinear shock modification and the spectrum of accelerated CRs particularly during the free expansion phase of a supernova remnant. The essential point is that the dilution of energy density as energetic particles fill an ever increasing volume in an expanding, spherical shock (which determines the cutoff energy of accelerated particles), produces qualitatively the same nonlinear effect as energetic particles escaping from the shock, as is parameterized in the planewave approximation. Thus, the shock evolution during this phase can be accurately represented as a sequence of quasistationary states.
 Publication:

26th International Cosmic Ray Conference (ICRC26), Volume 4
 Pub Date:
 1999
 Bibcode:
 1999ICRC....4..446E