The ^(54)Mn Clock and Its Implications for Cosmic Ray Propagation and Fe Isotope Studies
Abstract
Radioactive ^(54)Mn suggested as a 'clock' for measuring the lifetime of heavy cosmic rays, has a poorly known β-decay half-life estimated to be in the range from ~10^5 to 10 ^7 yr. Some years ago Koch et al. concluded from measurements of the Mn/Fe ratio that a significant fraction of low-energy (<1 GeV/nucleon) ^(54)Mn produced by Fe fragmentation had decayed. Using a propagation code that includes improved fragmentation cross-sections, and recent data from HEAO 3 and a number of other spacecraft, we have reexamined the evidence for ^(54)Mn decay in cosmic rays. We conclude that present cosmic-ray data cannot establish the degree of ^(54)Mn decay, but point out that this question has important implications for studies of the ^(54)Fe abundance in cosmic-ray source material, as well as for cosmic-ray propagation studies.
Additional Information
Copyright 1991 American Astronomical Society. Received 1990 August 27; accepted 1991 February 20. This work was supported in part by NASA under grants NAG8-678, NAG5-722, and NAGW-1919. We appreciate the assistance of T. L. Garrard with the propagation calculations. Some of this work was performed while B. T. Hayes was the recipient of a Caltech Summer Undergraduate Research Fellowship (SURF).Additional details
- Eprint ID
- 45629
- DOI
- 10.1086/170395
- Resolver ID
- CaltechAUTHORS:20140509-084205965
- NAG8-678
- NASA
- NAG5-722
- NASA
- NAGW-1919
- NASA
- Summer Undergraduate Research Fellowship (SURF), Caltech
- Created
-
2014-05-09Created from EPrint's datestamp field
- Updated
-
2021-11-10Created from EPrint's last_modified field
- Caltech groups
- Space Radiation Laboratory
- Other Numbering System Name
- Space Radiation Laboratory
- Other Numbering System Identifier
- 1990-15