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The ratio between secondary and primary cosmic ray particles is the mainsource of information about cosmic ray propagation in the Galaxy. Primarycosmic rays are thought to be accelerated mainly in Supernova Remnant (SNR)shocks and then released in the interstellar medium (ISM). Here they producesecondary particles by occasional collisions with interstellar matter. As aresult, the ratio between the fluxes of secondary and primary particles carriesinformation about the amount of matter cosmic rays have encountered duringtheir journey from their sources to Earth. Recent measurements by AMS-02revealed an unexpected behaviour of two main secondary-to-primary ratios, theBoron-to-Carbon ratio and the anti-proton-to-proton ratio. In this work wediscuss how such anomalies may reflect the action of two phenomena that areusually overlooked, namely the fact that some fraction of secondary particlescan be produced within the acceleration region, and the non-negligibleprobability that secondary particles encounter an accelerator (and arereaccelerated) during propagation. Both effects must be taken into account inorder to correctly extract information about CR transport fromsecondary-to-primary ratios.

Effects of reacceleration and source grammage on secondary cosmic rays spectra