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The Cosmic Ray Path Length Distribution Expected from the Local Space and Time Dependent Supernova Distribution

ACE/CRIS's high precision cosmic ray isotopic and elemental abundance measurements now allow us to test quantitatively cosmic ray source injection and transport models, such as the FIP versus volatility injection biases, the interstellar versus supernova dust grains, and decay versus nondecay of K-capture radionuclei, that can all provide important new constraints on the origin of cosmic rays. However, the standard leaky box model or other general Galactic models cannot provide the level of precision now required for analysing the ACE/CRIS measurements. We now need to investigate the local cosmic ray transport, spallation and reacceleration in the context of the local (~ kpc) interstellar medium and the local, relatively recent (<30 Myr) distribution of supernova sources. Thus, we propose to construct the local spacetime dependent distribution of supernovae as a source of shock energy, as well as potential particles, together with a model of the local space and time dependent inhomogeneous interstellar medium, using a wide variety of recent astronomical observations and theory. We will incorporate these distributions into a time dependent, three-dimensional Monte Carlo propagation program to determine the local cosmic ray path length distributions as functions of cosmic ray particle mass and energy, that are essential to understanding the cosmic ray local composition. This we will use in conjunction with nuclear spallation and reacceleration calculations to carry out analyses of isotopic and elemental measurements from ACE/CRIS in order to test propagation models and distinguish between between cosmic ray source injection models. We will also make these distributions available to others interested in making independent propagation calculations.


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Last Updated: 15 September, 1998

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