Solar minimum spectra of galactic cosmic rays and their implications for models of the near-earth radiation environment

A. J. Davis, R. A. Mewaldt, C. M.S. Cohen, A. C. Cummings, J. S. George, R. A. Leske, E. C. Stone, M. E. Wiedenbeck, N. E. Yanasak, E. R. Christian, T. T. Von Rosenvinge, W. R. Binns, P. L. Hink

Research output: Contribution to journalArticlepeer-review

22 Scopus citations


The radiation dose from galactic cosmic rays during a manned mission to Mars is expected to be comparable to the allowable limit for space shuttle astronauts. Most of this dose would be due to galactic cosmic rays with energies < 1 GeV nucleon-1, with important contributions from heavy nuclei in spite of their low abundance relative to H and He. Using instruments on NASA's Advanced Composition Explorer (ACE) spacecraft, we have made the most statistically precise measurements to date of the solar minimum energy spectra of cosmic ray nuclei with charge Z = 4-28 in the energy range ∼40-500 MeV nucleon-1. We compare these measurements obtained during the 1997-1998 solar minimum period with measurements from previous solar minima and with models of the near-Earth radiation environment currently used to perform shielding and dose calculations. We find that the cosmic ray heavy-element spectra measured by ACE are as much as 20% higher than previously published solar minimum measurements. We also find significant differences between the ACE measurements and the predictions of available models of the near-Earth radiation environment, suggesting that these models need revision. We describe a cosmic ray interstellar propagation and solar modulation model that provides an improved fit to the ACE measurements compared to radiation environment models currently in use.

Original languageEnglish (US)
Article number2000JA000325
Pages (from-to)29979-29987
Number of pages9
JournalJournal of Geophysical Research: Space Physics
Issue numberA12
StatePublished - Dec 1 2001
Externally publishedYes

ASJC Scopus subject areas

  • Geochemistry and Petrology
  • Geophysics
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science
  • Atmospheric Science
  • Astronomy and Astrophysics
  • Oceanography


Dive into the research topics of 'Solar minimum spectra of galactic cosmic rays and their implications for models of the near-earth radiation environment'. Together they form a unique fingerprint.

Cite this