Ionisation as indicator for cosmic ray acceleration
  Astrospheres and wind bubbles of massive stars are believed to be sources of cosmic rays with energies $E\lesssim 1\,$TeV. These particles are not directly detectable, but their impact on surrounding matter, in particular ionisation of atomic and molecular hydrogen, can lead to observable signatures. A correlation study of both gamma ray emission, induced by proton-proton interactions of cosmic ray protons with kinetic energies $E_\mathrm{p}\ge 280\,$MeV with ambient hydrogen, and ionisation induced by cosmic ray protons of kinetic energies $E_\mathrm{p}< 280\,$MeV can be performed in order to study potential sources of (sub)TeV cosmic rays. 
Florian Schuppan, Christian R\"oken, Natalie Fedrau, Julia Becker Tjus
astro-ph.HE