Abstract We have developed a new model for the production and propagation of spectrally resolved primary and secondary cosmic-ray (CR) nucleus elements within the framework of the Cosmic Ray Energy Spectrum module of the PIERNIK MHD code. We extend the algorithm to several CR nuclei and demonstrate our code’s capability in modeling primary and secondary CR species simultaneously. Primary C, N, and O are accelerated in supernova (SN) remnants. The spallation collisions of the primary nuclei against the thermal interstellar medium (ISM) protons lead to secondary Li, Be, and B products. All the CR species evolve according to the momentum-dependent Fokker–Planck equations that are dynamically coupled to the MHD system of equations governing the evolution of the ISM. We demonstrate the operation of this system in a gravity-stratified box reproducing the Milky Way conditions in the Sun’s local environment. We perform a parameter study by investigating the impacts of the SN rate, the CR parallel diffusion coefficient D ∥ , and the rigidity-dependent diffusion coefficient power index δ . A novel result of our investigation is that the secondary-to-primary flux ratio B/C increases with the increasing diffusion coefficient, due to the weaker vertical magnetic field resulting from CR buoyancy effects. Moreover, a higher SN rate leads to lower values of B/C, because of stronger winds and the shorter residence time of primary CR particles in dense disk regions.
Baldacchino-Jordan et al. (Tue,) studied this question.