Where the granular flows bend

TL;DR

This paper reports a new phenomenon in solar granulation where spectral line widths become extremely small at the boundary between granules and intergranular lanes, linked to flow bending, using high-resolution IMaX/Sunrise data and simulations.

Contribution

It identifies and explains a previously undetected spectral line width variation associated with flow bending in solar granulation.

Findings

Spectral line width sharply decreases at flow bending regions.

High-resolution data is crucial for detecting this phenomenon.

Simulations support the observational interpretation.

Abstract

Based on IMaX/Sunrise data, we report on a previously undetected phenomenon in solar granulation. We show that in a very narrow region separating granules and intergranular lanes the spectral line width of the Fe I 5250.2 A line becomes extremely small. We offer an explanation of this observation with the help of magneto-convection simulations. These regions with extremely small line widths correspond to the places where the granular flows bend from mainly upflow in granules to downflow in intergranular lanes. We show that the resolution and image stability achieved by IMaX/Sunrise are important requisites to detect this interesting phenomenon.