Snapshots of the evolution of the system during the generation of a mild straight jet (top row) and a very energetic helical jet (bottom row) for the β = 0.025 simulation. The resp. [purple/pink] field lines, which are initially resp. [closed/open], are plotted from fixed points along the bottom boundary resp. [on a circle of radius 1.5L₀/along the y = 0 axis]. The isosurface of the plasma density equal to is color-coded according to the vertical velocity component v_z: red indicates downward velocity, and blue upward. For comparison, the initial uniform density and the ambient Alfvén speed ĉ_A = 0.28. The simulation domain extent is [−12L₀;12L₀] × [−12L₀;12L₀] × [0;24L₀].