Origin of line broadening in fading granule: influence of small-scale turbulence

Abstract

In the quiet region of the solar photosphere, turbulent convective motions of the granular flows naturally drive the subgranular-scale flows. However, evaluating such small-scale velocities is challenging because of the limited instrumental resolution. Our previous study, Ishikawa et al. (2020), found line broadening events during fading process of granules; however, their physical mechanism has remained unclear. In the present study, we observed the fading granules with the Hinode-SOT/SP and performed spectral line inversions. Moreover, we investigated broadening events of synthesized spectra in fading granules reproduced by the MURaM simulation. Our results demonstrated that the small-scale turbulent motions are excited in the fading process and such turbulent flows contribute to line broadening. The spectral line widths can be potential tracers of the photospheric turbulent flows.