Granulation Flows over the Solar Cycle: Insights from Spectral Line Inversions

The change in the distribution of the magnetic field in the quiet Sun photosphere over the solar cycle might reasonably be expected to cause systematic variations in the photospheric thermodynamic structure. This could be due to changes in the dynamics of the convective overshoot or variations in the radiative properties. To look for such changes, we use high spatial and spectral resolution spectropolarimetric observations obtained by Hinode Solar Optical Telescope (SOT) and apply the Spectropolarimetric Inversions Based on Response Functions (SIR) code to infer physical conditions in the lower solar photosphere. By using many homogeneous datasets acquired over 15 years, we analyze the distributions of the inferred atmospheric parameters in the granules and intergranules of quiet Sun spectra throughout the solar cycle. The final goal of our study is to characterize changes in the inferred atmospheric profiles, in particular, the temperature structure, the line-of-sight velocities. Finally, we examine whether the trends we find correspond to physical modifications in the photosphere or might be due to long-term changes in the Hinode spectropolarimeter.