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Space Science Reviews

, Volume 130, Issue 1–4, pp 335–340 | Cite as

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

  • R. A. LeskeEmail author
  • R. A. Mewaldt
  • C. M. S. Cohen
  • A. C. Cummings
  • E. C. Stone
  • M. E. Wiedenbeck
  • T. T. von Rosenvinge
Article

Abstract

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 (34<Z<40)/O ratio on average more than 50 times higher in 3He-rich events than in LSEP events. At energies >10 MeV/nucleon, the most extreme event in terms of UH composition detected so far took place on 23 July 2004 and had a (34<Z<40)/O enhancement of ∼250–300 times the standard solar value.

Keywords

Sun: abundances Sun: particle emission Sun: coronal mass ejections (CMEs) Sun: flares 

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Copyright information

© Springer Science+Business Media B.V. 2007

Authors and Affiliations

  • R. A. Leske
    • 1
    Email author
  • R. A. Mewaldt
    • 1
  • C. M. S. Cohen
    • 1
  • A. C. Cummings
    • 1
  • E. C. Stone
    • 1
  • M. E. Wiedenbeck
    • 2
  • T. T. von Rosenvinge
    • 3
  1. 1.Space Radiation LaboratoryCalifornia Institute of TechnologyPasadenaUSA
  2. 2.Jet Propulsion LaboratoryCalifornia Institute of TechnologyPasadenaUSA
  3. 3.NASA/Goddard Space Flight CenterGreenbeltUSA

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