  The strong shocks in young supernova remnants (SNRs) should accelerate cosmic
rays (CRs) and no doubt exists that relativistic electrons are produced in
SNRs. However, direct evidence that SNRs produce CR nuclei depends on seeing an
unambiguous pion-decay feature and this has not yet been obtained.
Nevertheless, the lack of an observed pion-decay feature does not necessarily
mean that CR ions are not abundantly produced since ions do not radiate
efficiently. If CR ions are produced efficiently by diffusive shock
acceleration (DSA), their presence will modify the hydrodynamics of the SNR and
produce morphological effects which can be clearly seen in radiation produced
by electrons.
