Top panel: cuts of the radial field structure close to the HCS for three of the simulations. Dashed lines shows formulation (1) using ﹩| A| \,=| {B}_{Z}(R=5,Z=2)| ﹩ and the best fit for a. Bottom panel: aspect ratio a/L of the current sheet as a function of the Lundquist number for all six simulations. The plain blue line is obtained using L = 4R_⊙ and the shaded area spans L ∈ [2R_⊙, 6R_⊙]. The critical aspect ratio a/L = S^−1/3 is shown in plain black, while the Sweet–Parker aspect ratio a/L = S^−1/2 is represented with the dashed line.