New very local interstellar spectra for electrons, positrons, protons, and light cosmic ray nuclei

Abstract

The local interstellar spectra (LISs) for galactic cosmic rays (CRs) cannot be directly observed at the Earth below certain energies, because of solar modulation in the heliosphere. With Voyager 1 crossing the heliopause in 2012, in situ experimental LIS data below 100 MeV/nuc can now constrain computed galactic CR spectra. Using galactic propagation models, galactic electron, proton, and light nuclei spectra can now be computed more reliably as LISs. Using the Voyager 1 observations made beyond the heliopause, and the observations made by the PAMELA experiment in Earth orbit for the 2009 solar minimum, as experimental constraints, we simultaneously reproduced the CR electron, proton, helium, and carbon observations by implementing the GALPROP code. Below about 30 GeV/nuc solar modulation has a significant effect and a comprehensive three-dimensional (3D) numerical modulation model is used to compare the computed spectra with the observed PAMELA spectra at these energies. Subsequently the computed LISs can be compared over as wide a range of energies as possible. The simultaneous calculation of CR spectra with a single propagation model allows the LISs for positrons, boron, and oxygen to also be inferred. This implementation of the comprehensive galactic propagation model (GALPROP), alongside a sophisticated solar modulation model to compute CR spectra for comparison with both Voyager 1 and PAMELA observations over a wide energy range, allows us to present new self-consistent LISs (and expressions) for electrons, positrons, protons, helium, carbon, boron, and oxygen for the energy range of 3 MeV/nuc–100 GeV/nuc