Propagation of cosmic-ray nucleons in the Galaxy

We describe a method for the numerical computation of the propagation of pr imary and secondary nucleons, primary electrons, and secondary positrons an d electrons. Fragmentation and energy losses are computed using realistic d istributions for the interstellar gas and radiation fields, and diffusive r eacceleration is also incorporated. The models are adjusted to agree with t he observed cosmic-ray B/C and Be-10/Be-9 ratios. Models with diffusion and convection do not account well for the observed energy dependence of B/C, while models with reacceleration reproduce this easily. The height of the h alo propagation region is determined using recent Be-10/Be-9 measurements a s >4 kpc for diffusion/convection models and 4-12 kpc for reacceleration mo dels. For convection models, we set an upper limit on the velocity gradient of dV/dz < 7 km s(-1) kpc(-1). The radial distribution of cosmic-ray sourc es required is broader than current estimates of the supernova remnant (SNR ) distribution for all halo sizes. Full details of the numerical method use d to solve the cosmic-ray propagation equation are given.