Estimation of elemental abundances of heavy cosmic-ray primaries at the top of the atmosphere using plastic emulsion chamber and the derived source spectrum from the steady-state leaky box model

Abstract

Final results of the experiment for the estimation of charge abundances using plastic emulsion chamber consisting of CR-39 (HCB) and Fuji ET-7B nuclear-emulsion sheet, launched from Alice Springs for 32 hours at an atmospheric depth of 9.8 g cm−2 is presented. The latest long hour etching technique was used for track detection in plastics. The estimated reduced etch rate distribution presented was based on 2968 measured track diameter data in CR-39 (HCB) stacks. The observed charge spectrum from the reduced etch rate distribution was duly corrected for the top of the atmosphere by adopting the conventional formulation for cosmic-ray propagation along with the latest modified partial cross-sections for A-A collisions after Tsaoet al. The average value of the observed energy of the 77 very heavy primaries was estimated from the opening angle measurements of alpha fragments in Fuji ET-7B nuclear emulsion and was found to be 5.01 GeV/n which comes out to be 8.2 GeV/n, when corrected for the top of the atmosphere due to propagation in the residual atmospheric depth. The measured integral fluxes for NeMgSi and Fe groups above 4 GeV/n have been compared with the global data surveyed by Ichimuraet al. Our results on element/Si and element/Fe have been compared with the HEAO-3-C2 data after Englemannet al. Using SSLB model, the source abundance is derived from the observed result and that was compared with the results of Juliusson,et al., Lezniak and Webber and Garcia-Munozet al.