ON THE DETECTION OF SHOCKS IN THE SOLAR GRANULATION

We investigate the spectral signature of a hydrodynamic simulation of solar granulation and compare it with high resolution observations. Th e model gives the correct qualitative trend of increasing line width w ith decreasing continuum intensity seen by Nesis et al. (1992) and int erpreted by them as a sign of post-shock turbulence. We find, however, that the profiles in the dark downflow lanes are broader even when th ere is no horizontal transonic flow dr shock in the vicinity. We concl ude that the observations of Nesis et al. do not provide any firm evid ence for the presence of granular transonic flows. Nevertheless, the s imulation predicts a promising diagnostic of shocked horizontal flows. We find that at the locations of the shocks the line profiles are par ticularly broad, especially near the solar limb. We present observatio ns of quiet solar regions that show this specific signature of shocks and thus support the theoretical prediction of transonic granular flow s.