Magnetic field lines of a mixed CH and AR model. The CH is located at x₁ = 0, and the AR is represented by equal opposite-polarity sources located at x₁ = h and x₂ = 2h, where x₀ = h. The differences between the two panels are due to the polarity of the left footpoint of the AR with respect to the CH: positive in the top panel, and negative in the bottom panel. This creates an X-point.