Galactic Cosmic Rays Access to the Magnetosphere of Saturn

The megaelectron volt proton radiation belts of Saturn are isolated from the middle and outer magnetosphere, and the source of these high-energy protons is thought to be linked to the access of galactic cosmic rays (GCRs) in the system. To validate this hypothesis, it is first of all necessary to determine the realistic spectrum of GCRs at Saturn. Previously, only analytical attempts were performed in order to calculate the GCR spectra. In this letter we provide for the first time the numerical solution for the determination of the GCR access to the upper atmosphere and rings of Saturn. The proposed method is based on the charged particle tracing technique. As a result the GCRs access energies to the atmosphere and to the equatorial plane of the magnetosphere as a function of radial distance to the planet were obtained and the GCRs spectra were reconstructed. Dependencies of the spectral parameters such as the time or the incidence direction were also obtained offering all necessary information for simulating the interaction of GCRs with the Saturnian system during different phases of the Cassini mission. Plain Language Summary In this research letter we propose the numerical solution for the calculation of the galactic cosmic rays (GCRs) access energies to Saturn and its magnetosphere. Previously, only analytical approach was used to address this problem in the Saturnian system providing uncertain results. The new numerical approach on the basis of particle tracing brings much more accurate access energies, GCR spectra, and integrated GCR flux to the planet and across the magnetosphere and allows to estimate the Cosmic Ray Albedo Neutron Decay process on Saturn, calculate its contribution to the Saturnian radiation belts, and evaluate the impact of GCRs on the atmosphere, rings and moons of Saturn.