Eisenmeteorite als Raumsonden für die Untersuchung des Intensitätsverlaufes der kosmischen Strahlung während der letzten Milliarden Jahre

Abstract

The use of iron meteorites for the establishment of possible long-time variations (108 —109 years) of the cosmic ray intensity in interplanetary space is based upon the study of the production rates of nuclides which are formed by the interaction of cosmic ray particles with nuclei in meteorites. Mass spectrometric measurements of the isotopic composition of meteoritic potassium * are combined with data on cosmogenic rare gases and other elements to give K41-K40-exposure ages and rare gas production rates. The K41-K40-exposure ages are larger than the exposure ages obtained from the study of short-lived activities (e. g. Cl36, A39), by a factor 1.3 to 1.8. This result indicates that the cosmic ray intensity increased during the bombardment history of the meteorites. The data, for example, are consistent with the following assumptions: 1) The cosmic ray intensity was constant during most of the bombarding time and increased by a factor of about 1.5 only a few million years ago. 2) The intensity rose as I(t) =I0 e— γt with —1.1·10-9 ≦ γ ≦ —0.6 · 10-9 a–1. The consequences of this result for the interpretation of meteorite data are discussed.