Top-left: the spatial distribution of the vertical component of the forces for α = 0.4 and t = 60   min: total force (solid line), Lorentz force (dotted line) and −∇P_g − ρg force (dashed line). The dashed vertical line marks the position of the flux rope’s axis. Bottom-left: the same for α = 0.3 and t = 51.6   min. Top-right: close-up of the total force distribution for the two experiments: α = 0.4, t = 60   min (solid line) and α = 0.3, t = 51.6   min (dashed line). Bottom-right: density distribution, ρ(0,0,z), along height for the same experiments and times: α = 0.4 (solid line) and α = 0.3 (dashed line).