We study the production of cosmic rays ( CRs ) in supernova remnants ( SNRs ) , including the reacceleration of background galactic cosmic rays ( GCRs ) — thus refining the early considerations by Blandford & Ostriker ( 1980 ) and Wandel et al .
( 1987 ) — and the effects of the nuclear spallation inside the sources ( the SNRs ) .
This combines for the first time nuclear spallation inside CR sources and in the diffuse interstellar medium , as well as reacceleration , with the injection and subsequent acceleration of suprathermal particles from the postshock thermal pool .
Selfconsistent CR spectra are calculated on the basis of the nonlinear kinetic model .
It is shown that GCR reacceleration and CR spallation produce a measurable effect at high energies , especially in the secondary to primary ( s/p ) ratio , making its energy-dependence substantially flatter than predicted by the standard model .
Quantitatively , the effect depends strongly upon the density of the surrounding circumstellar matter .
GCR reacceleration dominates secondary CR production for a low circumstellar density .
It increases the expected s/p ratio substantially and flattens its spectrum to an almost energy-independent form for energies larger than 100 GeV/n if the supernovae explode on average into a hot dilute medium with hydrogen number density N _ { \mathrm { H } } = 0.003 cm ^ { -3 } .
The contribution of CR spallation inside SNRs to the s/p ratio increases with increasing circumstellar density and becomes dominant for N _ { \mathrm { H } } \raisebox { 2.0 pt } { $ > $ } \raisebox { -2.5 pt } { $ \sim$ } 1 cm ^ { -3 } , leading at high energies to a flat s/p ratio which is only by a factor of three lower than in the case of the hot medium .
Measurements of the boron to carbon ratio at energies above 100 GeV/n could be used in comparison with the values predicted here as a consistency test for the supernova origin of the GCRs .