Dimensionless emissivity J = 1 − R as a function of photon energy E for condensed Fe surface at B = 10¹³ G (top panel), B = 10¹² G and 10¹⁴ G (bottom panel), with magnetic field lines normal to the surface, for two angles of incidence θ_k = 0 and θ_k = π/4, as marked near the curves. Solid lines show our numerical results, and dashed lines demonstrate the fit. For comparison, dotted lines reproduce the simplified approximation used in Paper II.