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

TL;DR

This study investigates how small-scale turbulence during the fading of solar granules causes spectral line broadening, using observations and simulations to reveal turbulent motions as a key factor.

Contribution

It demonstrates that small-scale turbulent motions are excited during granule fading and contribute to line broadening, linking turbulence to spectral line width variations.

Findings

Small-scale turbulence is excited during granule fading.

Turbulent flows contribute significantly to line broadening.

Spectral line widths can trace photospheric turbulent flows.

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.