Initial conditions for the standard case (magnetic field properties alone; see Table 1). The three-dimensional picture on the top shows a sample of magnetic field lines (coloured according to the magnetic field strength). The plots below show the amplitude of the magnetic field components B_z and B_θ, the current density components J_z and J_θ (with J = ∇ × B/μ₀) and the twist angle as a function of the radial distance r to the flux-rope axis. All quantities are shown in dimensionless units; these can be converted into physical values (for our standard case) using the rightmost values in Table 1. Continuous lines represent the axial components (along ), while the dotted lines represent the azimuthal components (along ) of B and J.