Excellent spectrograms can yield observational insight in the dynamics of t
he solar surface not yet accessible to numerical simulations. We present re
sults of the elaboration of a series of spectrograms taken at the center of
the solar disk. Each of the spectrograms includes more than 250 granules,
while the series covers a time of 12 min. Our main emphasis is to study the
dynamics of the visible solar layers not only as a function of height but
also as a function of time.
We investigated the temporal and spatial behavior of the turbulent concentr
ation at the granular borders and its spreading out into the intergranular
space. In the deep photosphere, enhanced turbulence is concentrated predomi
nantly near granular borders, while at higher layers the turbulence spreads
out over the entire intergranular space. Remarkable is the decay of the tu
rbulence with the height in the photosphere. There was no significant varia
tion of the turbulence over the 12 min.
We also determined the rms turbulent pressure at the granulation layers nea
r tau(5000) = 1 The average ratio of turbulent to gas pressure is of the or
der of 0.1; values of this size are also discussed in recent theoretical wo
rks. In order to take the intermittency into account, we traced the peak to
peak variations of the turbulent velocity, which turn out to be approximat
e to 4 km sec(-1). The corresponding ratio of turbulent to gas pressure may
thus reach locally significant values up to about 0.3.
We did not find either a correlation or an anticorrelation between turbulen
ce and convective flow, although the turbulence is presumably generated by
granular shear flow. We suggest that the intermittent turbulence in the vis
ible layers and the convective flow constitutes a dynamical system. This tu
rbulence-granulation-dynamical system exhibits a cyclic behavior correspond
ing to the dynamical time of the granules, i.e. the growth and decay of the
ir velocity profile.
The power spectra of the turbulent and granular velocity show a two-compone
nt character, which presumably reflects the action of two different process
es determining the dynamics of the solar convective boundary layers and abo
ve.