Constraints on Cosmic Ray Confinement Time Using Cosmic Ray Radioactive Secondary Abundances from CRIS
Abstract
Secondary galactic cosmic rays are produced by fragmentation during transport through the interstellar medium(ISM). The abundances of β-decay radioactive secondaries depend on the time of propagation through a mean ISM density, which is a function of the decay halflife and the galactic confinement time τ_esc for propagation before escape out of the galaxy. Abundances of the β-decay species ^10Be, ^26Al, ^36Cl, and ^54Mn measured by the Cosmic Ray Isotope Spectrometer (CRIS) during the past two years predict a confinement time τ_esc ~ 20 Myr. The characteristic propagation volume probed by each radioactive secondary species depends on its decay time, and the range in decay halflives of these particular species provides a measure of the variation in the ISM density over different propagation volumes. Cosmic ray ^14C, with a decay lifetime ~ 1/2500× τ_esc, is sensitive to fragmentation occurring near the end of transport, probing inhomogeneities in the local ISM matter distribution. Abundance data for the β-decay secondaries from CRIS and interpretations using a simple cosmic ray transport model will be presented.
- Publication:
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APS April Meeting Abstracts
- Pub Date:
- April 2000
- Bibcode:
- 2000APS..APRW16007Y