In this model, particles are scattered across the shock fronts of a SNR, gaining energy at each crossing. Until the last two years, evidence to support this claim was circumstantial, based on theory and logic rather than on observations. For example, it seemed reasonable that SNR shocks could accelerate particles to the desired energies. In fact, in a sense, there is. The key is synchrotron radiation .
Synchrotron radiation is emitted when fast moving ions are accelerated in magnetic fields.
A magnetic field will force an energetic particle to travel in a helical path and emit radiation. We know that magnetic fields exist near and around SNR, for example in the ambient ISM or around the neutron star that can remain after a SNe. So if there are fast moving charged particles, they should produce synchrotron emission which we should be able to observe. The answer depends on a couple of factors. The energy of synchrotron emission depends on the energies of the fast charged particles doing the emitting and the strength of the magnetic field doing the bending.