Probability of λ, , for the 3D elliptical model, Eq. (2), for different aspect ratios, c/b, defined in the plane orthogonal to the shock propagation direction (see Fig. 2). The two dashed brown curves are the two analytical limits of Eqs. (4) and (5). The black dashed curve is the axisymmetric model of Janvier et al. (2015b) with a total angular width 2ϕ_max = 30°. The difference between the black and blue-brown dashed curves is that λ is computed from the local radial direction from the Sun for the first one and from the x-direction for the second (see Sect. 2.2). For all curves b/a = 1.4.