Magnitude of the total unsigned magnetic flux, Φ(t), at z = 0, plotted against time for simulations L1, L2 and L3 (the lower entropy, thin tube, ℛm ≈ 140 cases). The solid line corresponds to L1 (β = 1.5), the dotted line corresponds to L2 (β = 5), whilst the dashed line corresponds to L3 (β = 35). In each case, the flux has been normalised by the initial magnetic flux in the y-direction.