Diffusion coefficient and acceleration spectrum from direct measurements of charged cosmic ray nuclei

Abstract

We discuss the potentials of several experimental configurations dedicated to direct measurements of charged cosmic ray (CR) nuclei at energies ≳100 GeV/n. Within a two-zone propagation model for stable CRs, we calculate light primary and secondary nuclei fluxes for different diffusion and acceleration schemes. We show that the new detectors exploiting the long and ultra long duration balloon flights could determine the diffusion coefficient power index δ through the measurement of the boron-to-carbon ratio with an uncertainty of about 10–15%, if systematic errors are low enough. Only space-based or satellite detectors will be able to determine δ with very high accuracy even in the case of important systematic errors, thanks to the higher energy reach and the less severe limitations in the exposure. We show that no uncertainties other than those on δ affect the determination of the acceleration slope α, so that measures of light primary nuclei, such as the carbon one, performed with the same experiments, will provide valuable information on the acceleration mechanisms.