Inversion of a penumbral pixel (highlighted in Fig. 1 with a red square). In black, the simulated Stokes parameters, 𝕀^syn(λ), (left column) and atmosphere model parameters inverted in geometrical scale (X^syn(z), middle column) and in optical depth scale (X^syn(lgτ₅), rightmost column). The results of the inversion in hydrostatic equilibrium for the third and fourth cycle (see text), ) and ), are in solid red and dashed blue, respectively. The physical parameters inverted are T(z), v_LOS(z), B_x(z), B_y(z), and B_z(z). Since the height origin is not absolute (see Sect. 3.2), each atmosphere model is forced to have h(τ₅ = 1) = 1000 km. The atmosphere models are only shown between lg(τ₅) = 1.5 and lg(τ₅) = − 5 as the Stokes profiles, given the spectral line setup, are sensitive inside these optical depths, though the whole atmosphere is inverted. The shadowed area shows the lower limit errors for each physical parameter.