Modeling cosmic ray proton induced terrestrial neutron flux: A look-up table

Andrew C. Overholt, Adrian L. Melott, Dimitra Atri

Research output: Contribution to journalArticlepeer-review


Neutrons contribute a significant radiation dose at commercial passenger airplane altitudes. With cosmic ray energies > 1 GeV, these effects could, in principle, be propagated to ground level. Under current conditions, the cosmic ray spectrum incident on the Earth is dominated by particles with energies < 1 GeV. Astrophysical shocks from events such as supernovae accelerate high-energy cosmic rays (HECRs) well above this range. The Earth is likely episodically exposed to a greatly increased HECR flux from such events. Solar events of smaller energies are much more common and short lived but still remain a topic of interest due to the ground level enhancements they produce. The air showers produced by cosmic rays (CRs) ionize the atmosphere and produce harmful secondary particles such as muons and neutrons. Although the secondary spectra from current day terrestrial cosmic ray flux are well known, this is not true for spectra produced by many astrophysical events. This work shows the results of Monte Carlo simulations quantifying the neutron flux due to CRs at various primary energies and altitudes. We provide here look-up tables that can be used to determine neutron fluxes from proton primaries with kinetic energies of 1 MeV-1 PeV. By convolution, one can compute the neutron flux for any arbitrary CR spectrum. This contrasts with all other similar works, which are spectrum dependent. Our results demonstrate the difficulty in deducing the nature of primaries from the spectrum of ground level neutron enhancements. Key Points Astrophysical events increase cosmic ray flux on the Earth. Our tables which simulate the neutron flux of a variety of astrophysical events This is the first spectrum independent table

Original languageEnglish (US)
Pages (from-to)2765-2770
Number of pages6
JournalJournal of Geophysical Research: Space Physics
Issue number6
StatePublished - Jun 2013


  • cosmic rays
  • neutrons
  • terrestrial

ASJC Scopus subject areas

  • Space and Planetary Science
  • Geophysics


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