Lecturer: Mr. David Benyamin Affiliation: Racah Institute of Physics, The Hebrew University of Jerusalem Abstract: Over the years, significant effort has been devoted to the understanding of cosmic ray propagation in the galaxy, based on the energy dependence of the secondary to primary ratios in galactic cosmic rays. We developed a fully three dimensional numerical code describing the diffusion of cosmic rays in the Milky Way. This code enables us to explore a model in which a large fraction of the cosmic ray acceleration takes place in the vicinity of galactic spiral arms and that these spiral arms are dynamic. We recover different observed secondary to primary ratios. Moreover, we find that the particle density distributions become dependent on the energy, spectral indices of CRs become “harder” on one side of the spiral arm and “softer” on the other side, as is observed in pion produced gamma rays. Secondary to primary particle ratios, the effect on the K-capture isotopes are also reported, as is the present study of the positron fraction. Additional details of the upcoming Astrophysics' seminars can be found on the following link. ‏האירוע הזה כולל שיחת וידאו ב-Google Hangouts. הצטרף: https://hangouts.google.com/hangouts/_/mail.huji.ac.il/astrophysics?hceid=bWFpbC5odWppLmFjLmlsX2c0czhydDlpcmhwZzRvdGNybWIzZGFqcjdvQGdyb3VwLmNhbGVuZGFyLmdvb2dsZS5jb20.69lldqub9t3ftmfregnkvdkfe8&hs=121