Dynamics of the solar photosphere: THEMIS observations

We present the results of 2D narrow- and broad-band photometry of quiet granulation field as observed at the center of the Sun by the THEMIS telescope in IPM mode. The broad-band spectral images have been used to derive geometrical and statistical properties of the pattern produced by convective flows rising from deep layers of the Sun. The narrow-band spectral observations, in the C I 538.0 nm, Fe I 537.9 nm, and Fe I 557.6 nm photospheric lines, have been used to calculate velocity and intensity maps at different heights in the solar atmosphere. The auto-correlation functions of the velocity fields at different heights suggest that, near the solar surface, the dynamics resemble the behavior of a complex out-of-equilibrium system, characterized by a dynamical heterogeneity. Conversely, in the middle photosphere, where only one characteristic time exists, the dynamical heterogeneity disappears. Moreover, the characteristic scales, derived from photospheric velocity maps by means of wavelet and information entropy analysis', show a dependence of their properties on the formation height of photospheric lines and an enlargement of the velocity features with height.