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Studies of low-energy Galactic cosmic-ray composition at 22 AU. I - Secondary/primary ratiosData from the High Energy Telescope of the CRS experiment on Voyager 2 have been used to measure the intensity, spectra, and elemental abundances of Galactic cosmic rays from Be to Ni at about 100 MeV/n. The charge resolution of this telescope varies from sigma = 0.034 for oxygen to sigma = 0.11 for iron. The solar modulation deceleration parameter Phi relevant for these data is estimated to be around 300 MV (Phi = 150 MeV/n for particles with A/Z = 2), an unprecedently low level for such measurements. This low modulation parameter is a result of the measurements being made in the outer heliosphere at a heliocentric distance of 22 AU, and centered on the solar minimum period of cycle 21. The results on secondary/primary ratios are used to test the Leaky-Box model of cosmic ray propagation, using the most recent cross sections data in hydrogen and helium, and taking into account the effects of the ionized fraction of the interstellar medium. It is found that all the secondary/primary ratios up to P/S are completely consistent with an exponential pathlength distribution (PLD). This PLD shape also accounts for the Sc-V/Fe ratio.
Document ID
19910064379
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Ferrando, P.
(CEA Centre d'Etudes Nucleaires de Saclay, Gif-sur-Yvette, France)
Lal, N.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Mcdonald, F. B.
(Maryland, University College Park, United States)
Webber, W. R.
(New Mexico State University Las Cruces, United States)
Date Acquired
August 14, 2013
Publication Date
July 1, 1991
Publication Information
Publication: Astronomy and Astrophysics
Volume: 247
Issue: 1 Ju
ISSN: 0004-6361
Subject Category
Space Radiation
Accession Number
91A49002
Funding Number(s)
CONTRACT_GRANT: NGR-21-002-316
Distribution Limits
Public
Copyright
Other

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