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Published 2001 | public
Journal Article

Distinguishing galactic cosmic-ray source models with first ionization potential and volatility


Studies of the galactic cosmic-ray source composition reveal a pattern in the elemental abundances that may be controlled by the first ionization potential (FIP) or a closely correlated parameter, the condensation temperature (volatility). Determining the true parameter is key identifying the galactic cosmic-ray source (GCRS) material. Using data from the CRIS instrument onboard the ACE spacecraft, we examine five elements that are more volatile than other elements of similar FIP. Three of these (Na, Cu, Ge) show small deficits in their source abundances that may suggest a volatility-dependent fractionation. The source abundances of Ga and Zn (an intermediate FIP element) are consistent with either model. Possible systematic uncertainties from the cosmic-ray pathlength estimate as well as effects due to the instrumental acceptance are discussed. We also compare the GCRS composition to that observed in solar energetic particles.

Additional Information

© 2001 COSPAR. Published by Elsevier Science Ltd. Available online 3 August 2001. This work was supported by NASA at the California Institute of Technology (under grant NAG5-6912), the Jet Propulsion Laboratory, the Goddard Space Flight Center, and Washington University. We also wish to acknowledge many helpful comments from J.P. Meyer.

Additional details

August 19, 2023
October 17, 2023