Presentation #404.05 in the session Solar Interior.
Previous studies analyzing the evanescent nature of acoustic waves in the lower solar atmosphere (up to 300km above the photosphere) have shown an unexpected phase-shift of an order of 1s between different heights. These studies investigated the atomic absorption line Fe I 6173.3 Å, which is commonly used for helioseismic observations. Such phase-shifts can contribute to a misinterpretation of the measured travel time in local helioseismology, complicating estimations of, e.g., the deep meridional flow. In this study, we carry out phase-shift computations using a simulated, fully radiative and convective atmosphere (exhibiting naturally excited acoustic waves) from which the Fe I 6173.3 Å line is synthesized. The resulting phase-shifts across multiple heights indicate the presence of evanescent waves, similar to what is observed for real data. Comparing the Doppler-velocities, estimated from the synthesized absorption line with the true plasma velocities, we find substantial differences in phase-shifts as a function of height. This leads us to hypothesize that the non-adiabaticity of the solar atmosphere yields extra phase-shift contributions to Doppler-velocities. Such contributions must be considered for the accurate reconstruction of solar interior properties.