Investigation of the magnetic and temperature sensitivity of the Stokes parameters of absorption lines in the solar photosphere

TL;DR

This study calculates response functions of Stokes parameters in solar absorption lines to temperature, pressure, and magnetic field perturbations, revealing unique sensitivities useful for solar magnetic diagnostics.

Contribution

It introduces a method to estimate the response of Stokes profiles to physical condition changes using depression response functions and sensitivity indicators.

Findings

High excitation lines show increased temperature sensitivity.

V profile response is strongest under weak and intermediate magnetic fields.

Sensitivity indicators are provided for magnetic and temperature effects on lines.

Abstract

Response functions to perturbations in the temperature, pressure, microturbulent velocity, and magnetic intensity were calculated for the Stokes parameter profiles of the lines Fe I 525.06, 525.02 and Fe II 614.92 nm. The procedure proposed by Grossmann-Doerth, Larsson, and Solanki (1988) was used. We show that the depression response functions may be used not only to determine the depths at which changes in the physical conditions affect most effectively the absorption and emission in the continuum and in lines, but to estimate the response of Stokes profiles as well. The response was estimated using sensitivity indicators calculated as an integral of the response function over all photospheric layers. An anomalous temperature sensitivity was found for the Stokes profiles in lines with high excitation and ionization potentials such as the lines of O I, C I, Fe II. The depression of such lines increases rather than decreases with growing temperature. The magnetic sensitivity of Stokes profiles depends primarily on the magnetic field conditions. The response of V profiles is the greatest under the weak-field and intermediate-field conditions for photospheric lines with large values of the Lande factor, wavelength, and equivalent width. The results of calculations of sensitivity indicators are presented for magnetic lines together with the indices of magnetic and temperature enhancement.