Proton-Helium Spectral Anomaly as a Signature of Cosmic Ray Accelerator
  The much-anticipated proof of cosmic ray (CR) acceleration in supernova
remnants (SNR) must hinge on full consistency of acceleration theory with the
observations; direct proof is impossible because of the orbit scrambling of CR
particles. The PAMELA orbital telescope revealed deviation between helium and
proton CR spectra deemed inconsistent with the theory, since the latter does
not differentiate between elements of ultrarelativistic rigidity. By
considering an initial (injection-) phase of the diffusive shock acceleration
(DSA), where elemental similarity does not apply, we demonstrate that the
spectral difference is, in fact, a unique signature of the DSA. Collisionless
plasma SNR shocks inject more He2+ relative to protons when they are stronger
and so produce harder helium spectra. The injection bias is due to Alfven waves
driven by the more abundant protons, so the He2+ ions are harder to trap by
these waves because of the larger gyroradii. By fitting the p/He ratio to the
PAMELA data, we bolster the DSA-case for resolving the century-old mystery of
CR origin.
