How does the solar surface convection form the asymmetry in spectral profiles？

The solar surface, photosphere, consists of numerous bright cells called granule and surrounding dark channels called intergranular lane, which are consequence of plasma convection. This surface convection stores great deal of kinetic energy, a part of which may be converted and drive various types of physical phenomena appeared in the sun. Spectral profile integrating over whole the sun, observed as a star, has asymmetry, which is currently explained by such surface inhomogeneity of brightness and up/downward plasma motion, i.e., coupling between bright blue-shifted signal in granules and dark red-shifted signal in intergranular lanes. Our objective is to characterize precisely spectral profiles in granules and intergranular lanes, and to reveal what factors importantly contribute to induce the asymmetry in the solar spectra. We use the Hinodeʼs spectroscopic data that records the spectral profiles at Fe I 630.2 nm, in granules and intergranular lanes, separately. Each of the obtained absorption profiles shows ＼-directed and /-directed skewness, in granules and intergranular lanes, respectively. The former has never reported before, as only few studies reported a complicated profile (i.e., C-shape) in granule. Our calculation indicates that, spectral profiles in granules and intergranular lanes have already large asymmetry even before averaged over themselves, rather the integration process weakens their asymmetry. We would like to discuss what physical factors (e.g., intensity or/and flow speed) matter importantly to form the spectral asymmetry in the solar case, hoping that this can be applicable to obtaining the other starʼs convection properties as late-type stars generally show similar asymmetric profile.