Isotope production in meteorites and cosmic ray variations

Abstract

The depth profiles of cosmic ray tracks and radiisotopes such as ⁵³Mn, ²⁶Al, ⁶⁰Co etc measured in some chondrites indicate that the isotope production rates axe a sensitive function of the size of the meteoroid and depth within it. Based on these data the source functions of several stable and radioative isotopes in meteoroids having radii in the range of about 6 to 100 cm are computed. The production rates of ²¹Ne and ²²Ne enable us to calculate the exposure ages correctly and identify meteorites with complex exposure history. The radionuclide data in meteorites are examined in view of these production estimates. Except for the solar cycle modulation in galactic cosmic ray fluxes which is probably different in different regions of the he1iosphere, there are no definite indications of any significant long term time variations in GCR fluxes.