Cosmic-ray density per unit energy dn_CR/dE as a function of the radial coordinate r (horizontal axis) and the CR energy E (vertical axis) for cases 2 (panel a) and 4b (panel b) specified in Table 1. The color scale gives log₁₀(E^7/3r^ξdn_CR/dE) in cgs units (with ξ = 4/3 in panel a and ξ = 1.3 in panel b), and the dashed lines mark the boundaries between the three CR transport regimes discussed in the text, namely the low-energy diffusion (LED), high-energy diffusion (HED), and advection-dominated (AD) regimes.