Top: ϕ-averaged plasma bulk Lorentz factor in the striped wind region within 80° ≤θ ≤ 100° as a function of radius Γ(r). The dotted black line is the monopole prediction, . The dashed green line is the Michel magnetization parameter, μ_M (see Eq. (11)), to the power 1/3. The fast magnetosonic point is located at the yellow star, where . Bottom: θ-dependence of Γ(θ). Vertical dashed lines delimit the extension of the striped wind region. The black dotted line is a sinθ profile, as expected from the monopole solution.