Photospheric line asymmetry and granular velocity models.

We analyze spectral line profiles obtained from regions of the solar surface exhibiting either an upflow or a downflow on a spatial and temporal scale corresponding to the white-light granulation. The differences between their line bisectors are measured to quantify changes in the asymmetry of the profile resulting from granular motion. The observed bisector differences are compared with differences predicted using conflicting granular models. Models, in which the motion of large, long-lived granules decreases rapidly with increasing height in the photosphere, are compatible with the observed line profile asymmetries. [ABSTRACT FROM AUTHOR]