  We present a numerical extension to the analytical propagation model
introduced in Hein and Spanier (2008) to describe the leptonic population in
the galactic disc. The model is used to derive a possible identification of the
components that contribute to the leptonic cosmic ray spectrum, as measured by
PAMELA, Fermi and HESS, with an emphasis on secondary e+ - e- production in
collisions of cosmic ray particles with ambient interstellar medium (ISM). We
find that besides secondaries, an additional source symmetric in e+ and e-
production is needed to explain both the PAMELA anomaly and the Fermi bump,
assuming a power-law primary electron spectrum. Our model also allows us to
derive constraints for some properties of the ISM.
