SPAW as a function of the radial distance. Black symbols show the SPAW inferred from exact solutions of the Fokker-Planck equation 1 for a radial density profile. Circles show the result when considering Coulomb collisions as the only scattering process; squares show the result when Coulomb collisions and a turbulent scattering process with λ_turb = 1 AU are considered. Full lines of different colors show analytical approximations for various scattering processes and the total SPAW (red). The dashed lines are the approximate solutions in the limit r ≫ r₀. The vertical dashed line shows the prediction Eq. (22) of the distance of minimal SPAW. The parameters are r₀ = 1R_⊙, r_* = 1 AU, n_* = 5 cm⁻³, and lnΛ = 27. The electron energy is 150 eV.