Dependence of the energy components of Hamiltonian (3) on the radius R, along the spiral branches (in logarithmic scale): T is kinetic energy, Φ₀ is the axially symmetric potential, and ℋ is the Jacobi integral. Two spiral branches of the perturbation Φ₁ are defined by ϕ₀ = 0 and ϕ₀ = π (see Eq. (12)). The amplitude of the minima of the potential (ϕ₀ = 0) falls by two orders of magnitude from its maximum to the escape radius (outer vertical dashed line). The falling is almost exponential after R ≅ 6 kpc. We note that our model does not account for additional structures in the region below R = 3 kpc (inner dashed line), for instance, the Galaxy’s bar.