B.5 Calculation of ∥∇ ρ∥

So far the only restriction over the radial coordinate ρ is that it is a monotonic flux function going from 0 at the center to 1 at the edge. In the code we take ρ(ψ ) = r(ψ, 0) ∕ap where r is defined as a function of (ψ, θ) and ap = r(ψ  ,0)
   a. Using

(144)

we find

(145)