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Published 2002 | public
Journal Article

Fractionation of solar energetic particles and solar wind according to first ionization potential


Although it is well known that solar energetic particles are depleted in elements with first ionization potential (FIP) greater than ∼10 eV, it is less well known that the degree of FIP fractionation varies from event to event. Similar fractionation patterns and variations are observed in the solar wind, suggesting that these variations may have a common origin. We review evidence for the FIP-related fractionation of SEPs and compare it with FIP fractionation effects in the solar wind at 1 AU. On the basis of several significant differences between the solar wind and SEP compositions, we suggest that most solar energetic particles are not simply an accelerated sample of the average solar wind as observed at 1 AU; rather, solar particles and fast and slow solar wind appear to be distinct samples of coronal material with distinctly different FIP-fractionation patterns.

Additional Information

© 2002 COSPAR. Published by Elsevier Science Ltd. Available online 21 August 2002. This work was supported by NASA at the California Institute of Technology (under grant NAS5-6912), the Jet Propulsion Laboratory, and Goddard Space Flight Center.

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October 17, 2023