Upper panel: longitudinal width of the particle streaming zone for the simulations without (dashed lines) and with (solid lines) cross-field diffusion, 15.5 h after particle injection. Blue corresponds to case 1, orange to case 2, green to case 3, and red to case 4. Lower panel: longitudinal increase of the particle streaming zone at the lower (dashed) and upper (solid) longitude boundaries, 15.5 h after particle injection. The colour code follows the upper panel.