The Discrepancy in Modelling of Galactic Cosmic Ray Primaries and Secondaries

Given that the bulk of the galactic cosmic rays (CRs) originates from transient point-like sources, such as supernova remnants, the flux of the CR primary component measured at Earth depends on the local source history. Whereas the secondary omponent shows little to no variation due to nearby sources, and instead, should depend on the global distribution of CRs. Steady-state, rotational symmetric models (2D) of CR propagation assume smeared-out CR sources in the Galaxy and cannot properly take into account the influence of nearby point sources. In this paper, we infer evidence of nearby sources by illustrating that a 2D propagation model will not describe CR primaries and secondaries equally well. We adapted the 2D version of the GALPROP code to a compute-cluster environment and perform parameter studies comparing CR spectra with primary and secondary CR data separately. Doing a parameter study, one may expect different best fit values looking at the primary and secondary CR components separately, as it is unlikely that the source history mimicked by the 2D models coincides with the real local source history. We find that the primaries and secondaries are fitted with differing best fit parameters, with the results indicating that the 2D model being more suited to modelling secondary CRs. The insufficient modelling of primary CRs can be contributed to the possible presence of local CR sources.