Regularities in the response of spectral lines to small perturbations in physical quantities in the photosphere

Numerical simulations are used to establish a number of dependencies between small perturbations in physical quantities in the photosphere and small variations in the Stokes profiles of spectral lines. A perturbation of any physical quantity in the model photosphere shifts every point in a line profile in the direction perpendicular to the tangent to the profile at that point. The actions on the wing of a spectral line of perturbations in the magnetic field and radial velocity are equivalent for a particular ratio of these perturbations (if the line is fully split in the magnetic field). If the response of part of a line wing is considered as a shift in wavelength, the area under the curve representing the response to perturbations in the magnetic field and radial velocity has a simple physical meaning.