Diameter range of impacting planetesimals as a function of altitude for protoplanet core masses of 0.1 M_⊕ (panel a), 1 M_⊕ (panel b), and 3 M_⊕ (panel c) as a function of altitude. Grey areas denote ranges between the lower and upper limit of impacting mass bins (solid lines). The plot shows bolide velocities v_i with respect to altitude h with an impact velocity v_h=0 > v_drift. All simulations are carried out with a grid of initial bolide diameters ranging from 1 ≤ D₀ ≤ 10⁷ cm.