NONLINEAR DYNAMICS OF THE SOLAR GRANULATION - A 1ST APPROACH

The non turbulent or turbulent behaviour of overshooting convective motions in the solar photosphere is studied by analysing spatially highly resolved spectrograms. We calculate the variation of a function similar to the well known Liapunov exponent derived from several line parameters. When the data are filtered and the variation of the parameters is considered over subgranular scales (< 1arcsec) the Liapunov like exponents show a random variation at positive values. Normally, positive values of Liapunov exponents indicate chaotic motions, and our results are a hint that at subgranular scales the physics change which is in agreement with results from a coherence analysis between line parameters at several photospheric heights, the enhancement of the full width at half maximum in the intergranulum and model calculations that give evidence for the existence of a turbulent component of the temperature and velocity field.