UH cosmic rays and solar system material: The elements just beyond iron

The origin of the elements from Cu to As in the UH (ultra-heavy) cosmic rays is investigated and related to current concepts of the nucleosynthesis of solar system material. The charge spectrum of the UH cosmic rays in the interval 29Z60 is studied via a fully developed propagation calculation for source abundances given by solar system material, ther-process, the massive-star core helium-burnings-process, and explosive carbon burning. None of these sources considered individually can explain the cosmic ray observations. However a combination of material produced in ther-process, the core helium-burnings-process and in explosive carbon burning provides a good representation of the experimental data. The cosmic-rayr-process is found to differ from solar systemr-process events by an underproduction of the low-massr-process peaks relative to theA195 peak. The large cosmicray abundance forZ=40–44 may be due to anr-process fission component, but this explanation is by no means certain. Improved cosmic-ray data, especially for Zn–Sr, can provide limits to the various source contributions. The model described here gives a consistent picture for the origin of both the cosmic rays and the solar system elements just beyond iron, and adds additional evidence for the importance of massive stars as a site of nucleosynthesis and the birthplace of the cosmic rays.Enrico Fermi Institute.     

Radiative decay behind strong M.H.D. shocks

The effect of radiation up on the state of gas behind strong M.H.D. shock front has been studied. The jump conditions for flow variables across the shock boundary have been obtained and temperature decay behind the shock front is determined for a optically-thin brehmsstrahlung radiation plasma. It has been found that, for a shock within strong magnetic field, the temperature decay is much quicker.