High energy cosmic ray spectroscopy .1. Status and prospects

In a recent paper (Nature, 1996, submitted) we claimed that the 'bump' in the extensive air shower size spectrum near 10(6) particles is due to heavy nuclei from a comparatively local 'source'. The energy spectrum of this single source is of the shape advocated by Berezhko et al. (JETP 82 (1996) 1) for supernova remnants (SNR) and is characterized by, approximately, an E-2 spectrum up to an energy E-max followed by a rapid fail above. The SNR model makes specific predictions for E-max as a function of nuclear charge. If, as is likely, the CR nuclei are fully ionized, we must identify the 'bump' in the paper submitted to Nature with the CNO group of nuclei. We have, accordingly, searched for the corresponding bump due to iron at a bigger shower size. Analysis of the world's data so far leads us to claim its detection, although not, yet, at as high a level of significance as the first bump. Prospects for augmenting the size spectrum technique, for studying what we call this new branch of spectroscopy, are examined. (C) 1997 Elsevier Science B.V.