Relative temperature fluctuations vs. optical depth. Top panel: inversion results of SP (red line), GFPI (orange line) and Ca ii H data (blue line), and of the HD-FR simulation spectra (black-solid line). Overplotted are the relative temperature fluctuations in the HD-FR simulation box (black dashed-triple-dotted line) and the curve given in Hayek et al. (2010, HA10) for a simulation with continuum scattering (black-dashed line). Bottom panel: inversion results of SP/Ca ii H multiplied by two/five (red/blue lines), and the values from the simulations of Wedemeyer et al. (2004, WE04; black-dotted line), of HA10 with continuum scattering (black-dashed line) and of HA10 with continuum and line scattering (black-dash-dotted line).