Values of the parameter ζ [Eq. (B.7)] as a function of the magnetic field strength B and dimensionless temperature Θ_e. Here, we fix sin θ = 1. Our models always stay in the part of the plane located above the dashed horizontal red line (Θ_e > 5, where the approximation (B.1) is good) and below the dashed red contour (X > 10, where the approximation (B.3) is excellent). The solid white contours are level sets of ζ.