Cosmic Ray Source Abundances and the Acceleration of Cosmic Rays
J.S. George, A.C. Cummings, R.A. Leske, R.A. Mewaldt, E.C. Stone
	California Institute of Technology, Pasadena, California, USA
M.E. Wiedenbeck, N.E. Yanasak
	Jet Propulsion Laboratory, Pasadena, California, USA
W.R. Binns, P.L. Hink, J. Klarmann, M. Lijowski 
	Washington University, St. Louis, Missouri, USA
E.R. Christian, T.T. von Rosenvinge
	NASA / Goddard Space Flight Center, Greenbelt, Maryland, USA
The elemental abundances of galactic cosmic rays (GCRs) observed at Earth reflect the abundances at the source, and their evolution during propagation through the Galaxy. Careful modeling of the transport of cosmic rays through the intervening matter can yield an estimate of the elemental source composition and help to identify the nature of the source and acceleration mechanism. It has long been noted that the GCR elemental source abundances show a fractionation corresponding to their chemical properties. A similiar effect is observed in the solar wind and solar energetic particles. The first ionization potential (FIP) and the condensation temperature (volatility) are two possibilities for the parameter controlling the fractionation. For most elements these two quantities are well correlated with each other. A few elements break the general correlation of FIP and volatility and the abundances of these may help to distinguish between models of the pool of material from which the GCRs are accelerated. The Cosmic Ray Isotope Spectrometer (CRIS) instrument on ACE has been making measurements of local GCR abundances for about two years. These new data, combined with a leaky box propagation model, can provide new insight into the nature of the source and acceleration of galactic cosmic rays.