Dependency of the emerging spectra (left column) and atmospheric structure (right column) on the model parameters. The spectra are shown in energy flux times polar cap area, i.e., in luminosity units, for both polarization modes. From top to bottom, we show how the spectral shape and the structure of the atmosphere depend on the mass-accretion rate, Ṁ (a), the polar cap radius, r₀ (b), the cyclotron energy, E_cyc (c), and the fraction of the accretion energy going into nonthermal collisional excitations, f_cyc. The same baseline model is shown in purple in all panels. See text for further discussion.