The relative abundance of the isotopes of Li, Be and B and the age of cosmic rays

Propagation of cosmic rays in the galaxy

“…In Figure 4.14, the observed ratios of sub-iron group to iron-group of nuclei are shown as a function of energy as given by Garcia-Munoz (1973). In this figure, different authors (Smith, et al, 1973b;Juliusson, 1974;Webber, et al, 1973c; have used different criteria in defining the charge groups and the observed scatter of points does not permit any definitive conclusions to be drawn as in the case from * for power law spectra in rigidity (Smith et al, 1973a) ** for power law spectra in kinetic energy per nucleon variation from about 2 GeV/n down to 30 MeV/n. Thus one can infer from…”

“…(ii) In a similar fashion if one attributes the entire flux of the observed isotropic X-rays (Metzger et al, 1964) to the inverse Compton scattering of electrons filling all space, with photons of the universal black body radiation (Felten and Morrison, 1966), one notes that the flux of electrons needed is a factor of 40 or perhaps even 103 smaller (Longair, 1970) than what is known to exist in interstellar space. (iii) A study of the relative intensities of Be and B nuclei (Brown et al, 1973a;O'Dell et al, 1973;Webber et al, 1973a) and that of the spectral shape of cosmic ray electrons (Daniel and Stephens, 1967) strongly suggest that the residence time of cosmic rays in the storage space is less than 107 years whereas typical time scales involved in extragalactic models is about two orders of magnitude larger. (iv) From a detailed examination of the energetics involved in extragalactic models, Ginzburg and Syrovatskii (1964 have come to the conclusion that the energy density of cosmic rays in metagalactic space is likely to be exceedingly small compared to that in our galaxy.…”

“…If this were so then the genuine galactic radio emitting region will also be considerably flattened and approach closer to the size of the radio disk. Furthermore, recent observations on cosmic rays strongly suggest that the residence time of cosmic rays is likely to be less than 107 years (Brown et al, 1973a;Webber et al, 1973a;O'Dell et al, 1973;Daniel and Stephens, 1967). These observations would therefore indicate that even in the galactic model the effective cosmic ray storage region is the galactic disk.…”

“…In The ratio of secondary nuclei to iron group as a function of kinetic energy per nucleon; curve shown here is similar to that of Curve A in Figure 4.13. the atmosphere, as a function of kinetic energy per nucleon as summarized by Garcia-Munoz (1973) (Smith, et al, 1973b;Juliusson, 1974;Webber, et al, 1973c); included also by crosses are the results from Golden, et al (1973). For comparison, we have also shown in this figure two types of energy dependence, one varying as W -0 .…”

“…Here, E" is the energy of the particle when it gives rise to a particle t m of energy E' and Q, (E') is the production spectrum of em nucleus directly as a function of mean energy (Casse et al, 1971;Brown et al, 1973a; O 'Dell et al, 1973;Smith et al, 1973a;Webber et al, 1973a;Juliusson, 1974). Also shown in the figure are two curves A and B representing the calculated values of the ratio for complete survival and decay respectively of the 10Be produced.…”