  Trees of fragmenting granules (TFG) and associated flows are suspected to
playa major role in the formation of the network in the quiet Sun. We
investigate the counterparts, in terms of dynamics, of surface structures
detectable by high resolution observations in deeper layers up to 15 Mm, which
are only available from numerical simulations. The first aim is to demonstrate
that TFG can be evidenced either from surface intensitites, vertical (Vz), or
Doppler (Vdop) velocities. The second is to show that horizontal flows, which
are derived from intensities or Vz/Vdop flows, are in good agreement, and that
this is the case for observations and numerical simulations. The third
objective is to apply this new Vz-based method to a 3D simulation to probe
relationships between horizontal surface flows, TFG, and deep vertical motions.
The TFG were detected after oscillation filtering of intensities or Vz/Vdop
flows, using a segmentation and labelling technique. Surface horizontal flows
were derived from local correlation tracking (LCT) and from intensities or
Vz/Vdop flows. These methods were applied to Hinode observations, 2D surface
results of a first simulation, and 3D Vz data of a second simulation. We find
that TFG and horizontal surface flows (provided by the LCT) can be detected
either from intensities or Vz/Vdop component, for high resolution observations
and numerical simulations. We apply this method to a 3D run providing the Vz
component in depth. This reveals a close relationship between surface TFG (5 Mm
mesoscale) and vertical downflows 5 Mm below the surface. We suggest that the
dynamics of TFG form larger scales (the 15-20 Mm supergranulation) associated
with 15 Mm downflowing cells below the surface. The TFG and associated surface
flows seem to be essential to understanding the formation and evolution of the
network at the meso and supergranular scale.
