Temporal and Spatial Variations of Cosmogenic Radionuclide Production Rates in Chondrites During Their Passage Through the Inner Heliosphere

To study radiation environment in the interplanetary space, cosmogenic radionuclides in meteorites, the production rates of which are in direct proportionality to the intensity of cosmic rays, are used. The contents of cosmogenic radionuclides of different half-lives T1/2, measured in 42 stony meteorites (chondrites) having sequentially fallen onto the Earth during the period of 1959–2016, are analyzed. They are accumulated by the galactic cosmic rays (GCRs) along the orbits of the chondrites before their falls onto the Earth at some average heliocentric distances, depending on the size of the chondrite orbit and on T1/2 of the radionuclide. The comparison with the calculated production rates of radionuclides in the identical chondrites for isotropic irradiation by the GCRs at ~ 1 AU is demonstrated. The calculations are based on the stratospheric balloon monthly data on the GCR intensity [1] for the periods of accumulation of each radionuclide in each chondrite. The dependence of production rates of the radionuclides of different half-lives upon the GCR variations in the heliosphere is studied. The obtained long set of homogeneous data on cosmogenic radionuclide production rates in consecutively fallen chondrites provides the unique information on the space-time continuum of the cosmogenic radionuclide production rates and their variations over a long-time scale, which could be useful in the correlative analyses of processes in the inner heliosphere and, thus, in the forecast of radiation situation, which is important for the predicted manned flights.