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Published June 2007 | public
Journal Article

An Update on Ultra-Heavy Elements in Solar Energetic Particles above 10 MeV/Nucleon


Measurements below several MeV/nucleon from Wind/LEMT and ACE/ULEIS show that elements heavier than Zn (Z=30) can be enhanced by factors of ~100 to 1000, depending on species, in ^3He-rich solar energetic particle (SEP) events. Using the Solar Isotope Spectrometer (SIS) on ACE we find that even large SEP (LSEP) shock-accelerated events at energies from ~10 to >100 MeV/nucleon are often very iron rich and might contain admixtures of flare seed material. Studies of ultra-heavy (UH) SEPs (with Z>30) above 10 MeV/nucleon can be used to test models of acceleration and abundance enhancements in both LSEP and ^3He-rich events. We find that the long-term average composition for elements from Z=30 to 40 is similar to standard solar system values, but there is considerable event-to-event variability. Although most of the UH fluence arrives during LSEP events, UH abundances are relatively more enhanced in ^3He-rich events, with the (3410 MeV/nucleon, the most extreme event in terms of UH composition detected so far took place on 23 July 2004 and had a (34

Additional Information

© 2007 Springer Science + Business Media B.V. Received: 2 February 2007. Accepted: 10 April 2007. Published online: 24 May 2007. This work was supported by NASA at the California Institute of Technology (grant NAG5-12929), the Jet Propulsion Laboratory, and the Goddard Space Flight Center.

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