Fig. Magnetic field lines on q=1/10 magnetic surface (upper left), q=1/2 magnetic surface (upper right), q=1 magnetic surface (middle left), q=2 magnetic surface (middle right), q=3 magnetic surface (lower left), and q=4 magnetic surface (lower right). Source codes for producing these figures: p.sh and torus.sketch.
Fig. Left: 3D view of guiding-center motion in tokamak; Right: 2D poloidal view