NUMERICAL MODELING OF SPECTRAL-LINE ASYMMETRIES IN PHOTOSPHERIC STRUCTURES .1. QUIET SUN

Modelling of asymmetries in spectral lines with different formation he ights (K I 7699, Fe I 5576 and Fe I 5635 Angstrom), observed in the qu iet Sun at the disk center, has been performed with the aim of reprodu cing the absolute line bisectors obtained from low resolution observat ions. The influence of a number of physical and observational factors on the bisector shape and line shifts, acting together or separately, is discussed, e.g. mesogranular flows, waves, microturbulence, defecti ve temporal and spatial averages, etc. The simulations are based on th e VAL-C model (Vernazza et al. 1981) representing the mean photosphere , and the granular model by Nelson (1978). Following evidence in the l iterature, the best match to the observed absolute mean bisectors is o btained by including in the numerical code a gravity wave and a streng thening of the microturbulence in the lower layers of the intergranule .