Geometry of a loop composed of a semicircular central part of length L and apparent radius R (in blue), with two vertical legs of length L_c (in black). Vector s follows the magnetic axis of the loop, from left to right by convention. The electron temperature, density, and pressure are respectively indicated at the apex (s = L_c + L/2) as T_apex, n_apex, and P_apex, and at the top of the vertical legs (s = L_c and s = L_c + L) as T₀, n₀, and P₀.