Abundances of Z > 52 nuclei in galactic cosmic rays: longterm averages based on studies of pallasites.
Abstract
About 1200 fossil tracks due to ultraheavy (Z > 50) cosmicray nuclei have been studied in olivine crystals from two meteorites, Marjalahti (cosmicray exposure age 175 x 106 yr) and Eagle Station (50 x 106 yr). The track length data are analyzed in terms of relative abundances in the flux of Z > 52 elements in space of kinetic energy greater than 11.5 GeV per amu, taking into account all uncertainties due to effects such as annealing, space erosion, and nuclear fragmentation within the meteorites. The longest tracks in Marjalahti are of maximum recordable length 900 . If these tracks are assumed to be due to elements of 90 < Z < 96, the abundances of elements in four charge groups (52 < Z < 62, 63 < Z < 74, 75 < Z < 83, and 90 < Z < 96), relative to Fe group nuclei, are found to be 0.42 times the corresponding values in the solar system abundances. However, if the charge group assignment is made on the basis of extrapolation of known recordable lengths for accelerated Fe, Zn, Ge, and Kr ions, then the longterm average values of abundances in charge groups 5762, 6374, 7583, and 9096, relative to Fe group nuclei, are found to be 0.510 times the corresponding solar system ratios; in this case the largest abundance ratio ( 10 x) is found for actinide nuclei (90 < Z < 96). The present track length data allow one to place an upper limit of 1018 cm 2 s sr for the flux of magnetic monopoles of pole strength g = n (137 e/2) with n > 4. Subject headings: cosmic rays: abundances  cosmic rays: general  meteorites
 Publication:

The Astrophysical Journal
 Pub Date:
 November 1976
 DOI:
 10.1086/154826
 Bibcode:
 1976ApJ...210..258O
 Keywords:

 Abundance;
 Cosmic Rays;
 Heavy Nuclei;
 Meteoritic Composition;
 Olivine;
 Particle Tracks;
 Calibrating;
 Fossils;
 Germanium;
 Iron;
 Krypton;
 Magnetic Flux;
 Magnetic Poles;
 Zinc;
 Space Radiation