The VDA apparent path length (a) and solar injection time (b) of SEPs as a function of the heliolongitude for energy-dependent (Equation (7), yellow crosses) and constant (cyan hexagons) threshold fraction f(E) = 0.01, for moderate turbulence. In panel (a), the apparent path length s = −0.05 au for Δϕ = −60^∘ is omitted for clarity.