Determination of Radial-Tangential Macroturbulence Stratification in the Solar Photosphere

This study models the depth-dependent behavior of Radial-Tangential (RT) macroturbulent velocity fields in the solar photosphere using high-resolution Fourier-domain analysis. The purpose of this investigation is to determine the velocity stratification to provide a useful empirical benchmark for evaluating both classical one-dimensional models and modern three-dimensional hydrodynamical simulations. The method employs 14 carefully selected, unblended iron lines from the solar flux atlas, which are analyzed through a disk-integration technique while fixing the solar synodic equatorial rotation and microturbulent velocity. Findings reveal that the macroturbulent velocity is not a constant value; it exhibits an overall decline from approximately 4.0 km s−1 in the deeper photospheric layers at an optical depth of log ̄τ = −0.61 to 3.0 km s−1 in the upper atmospheric layers at an optical depth of log ̄τ = −1.47. This velocity gradient is consistent with the convective deceleration of solar granulation as it rises through the atmosphere. The results show good quantitative agreement with prior wavelength-domain studies, supporting the interpretation that the detected stratification represents a physical property of the photosphere rather than a numerical artifact. These established profiles offer a useful semi-observational constraint for testing modern solar atmosphere simulations.