Disclaimer: The following material is being kept online for archival purposes.

Although accurate at the time of publication, it is no longer being updated. The page may contain broken links or outdated information, and parts may not function in current web browsers.

Composition of Solar Energetic Particle Events as  Measured by ACE/ULEIS

Joseph R. Dwyer


Since its August 1997 launch, the Ultra-Low-Energy-Isotope (ULEIS) spectrometer onboard the ACE spacecraft has observed a large number of both gradual and impulsive solar energetic particle (SEP) events.  At 1 MeV/nucleon these events show remarkable variability of both the elemental and isotopic compositions.  We present new measurements of the 22Ne/20Ne ratio for these SEP events.  We have selected two subsets of the data according to whether 3He/4He > 0.01.  For the 3He-"poor" subset, we find that 22Ne/20Ne depends only weakly upon Fe/Mg and is marginally consistent with the solar wind value of 0.073.  The 22Ne/20Ne ratio for the 3He-"rich" subset, on the other hand, shows a significant correlation with Fe/Mg.  However, when compared with the elemental abundances, these variations in the 22Ne/20Ne ratio are much larger than expected from a simple charge to mass dependence, as was derived by Breneman & Stone (1985).

   Authors: J. R. Dwyer, G. M. Mason, J. E. Mazur, R. E. Gold and S.  M. Krimigis

  Organization: University of Maryland
     Telephone: 301-405-6208
           Fax: 301-314-9547
        e-mail: dwyer@uleis.umd.edu
       Address: Space Physics Group
   Department of Physics
   University of Maryland
   College Park, MD 20742

Above is background material for archival reference only.

NASA Logo, National Aeronautics and Space Administration
NASA Official: Adam Szabo

Curators: Robert Candey, Alex Young, Tamara Kovalick

NASA Privacy, Security, Notices