Initial state of the model AR variables, showing a cut in the x–z plane at y = 0 for the 3D dipole magnetic field with d = 2.5. (a) Initial density, ρ, and selected magnetic field lines. (b) Initial fast magnetosonic speed, Vf. The color map and contours show the spatial dependence of Vf. (c) Initial normalized background temperature, T. (d) Initial values of plasma β.