Dynamics of Trees of Fragmenting Granules in the Quiet Sun: Hinode/SOT Observations Compared to Numerical Simulation

TL;DR

This study compares observed and simulated trees of fragmenting granules in the quiet Sun, revealing that simulations can replicate key properties and suggesting their role in supergranulation and magnetic network formation, with minimal variation across solar cycles.

Contribution

It demonstrates that 3D magneto-convection simulations accurately reproduce the properties of trees of fragmenting granules observed by Hinode/SOT in the quiet Sun.

Findings

Simulations reproduce observed TFG properties such as lifetime, size, and motions.

Largest TFGs are linked to strong flows and may influence supergranulation.

No significant TFG variation between solar minimum and maximum was observed.

Abstract

We compare horizontal velocities, vertical magnetic fields and evolution of trees of fragmenting granules (TFG, also named families of granules) derived in the quiet Sun at disk center from observations at solar minimum and maximum of the Solar Optical Telescope (SOT on board Hinode) and results of a recent 3D numerical simulation of the magneto-convection. We used 24-hour sequences of a 2D field of view (FOV) with high spatial and temporal resolution recorded by the SOT Broad band Filter Imager (BFI) and Narrow band Filter Imager (NFI). TFG were evidenced by segmentation and labeling of continuum intensities. Horizontal velocities were obtained from local correlation tracking (LCT) of proper motions of granules. Stokes V provided a proxy of the qline of sight magnetic field (BLOS). The MHD simulation (performed independently) produced granulation intensities, velocity and magnetic field vectors. We discovered that TFG also form in the simulation and show that it is able to reproduce the main properties of solar TFG: lifetime and size, associated horizontal motions, corks and diffusive index are close to observations. Largest (but not numerous) families are related in both cases to strongest flows and could play a major role in supergranule and magnetic network formation. We found that observations do not reveal any significant variation of TFG between solar minimum and maximum.