Numerical modeling of galactic cosmic-ray proton and helium observed by AMS-02 during the solar maximum of solar cycle 24
Date
2019Author
Corti, Claudio
Potgieter, Marius S.
Bindi, Veronica
Consolandi, Cristina
Light, Christopher
Metadata
Show full item recordAbstract
Galactic cosmic rays (GCRs) are affected by solar modulation while they propagate through the heliosphere. The
study of the time variation of GCR spectra observed at Earth can shed light on the underlying physical processes,
specifically diffusion and particle drifts. Recently, the AMS-02 experiment measured with very high accuracy
the time variation of the cosmic-ray proton and helium flux between 2011 May and 2017 May in the rigidity
range from 1 to 60 GV. In this work, a comprehensive three-dimensional steady-state numerical model is used to
solve Parker’s transport equation and reproduce the monthly proton fluxes observed by AMS-02. We find that the
rigidity slope of the perpendicular mean free path above 4 GV remains constant, while below 4 GV, it increases
during solar maximum. Assuming the same mean free paths for helium and protons, the models are able to
reproduce the time behavior of the p/He ratio observed by AMS-02. The dependence of the diffusion tensor on the
particle mass-to-charge ratio, A/Z, is found to be the main cause of the time dependence of p/He below 3 GV
URI
http://hdl.handle.net/10394/31887https://iopscience.iop.org/article/10.3847/1538-4357/aafac4/pdf
https://doi.org/10.3847/1538-4357/aafac4