Magnetic field strength distribution from below the photosphere (− 5 Mm) to the corona (10 Mm). The vertical axis gives the height in Mm, and the horizontal axis gives the horizontal size in Mm. Height z = 0 represents the base of the photosphere. The red lines are the magnetic field lines, and the yellow dashed lines are the β = 1 contours (one on the photosphere and the other one around the null point).