  Microturbulence (\xi) is a key parameter introduced in stellar spectroscopy
to explain the strength of saturated lines by formally incorporating an
additional thermal broadening term in the line opacity profile. Although our
Sun can serve as an important testing bench to check the usual assumption of
constant \xi, the detailed behavior of how \xi varies from the disk center
through the limb seems to have never been investigated so far. In order to fill
this gap, local \xi values on the solar disk were determined from the
equivalent widths of 46 Fe I lines at 32 points from the center to the limb by
requiring the consistency between the abundances derived from lines of various
strengths. The run of \xi with \theta (angle between line of sight and the
surface normal) was found to be only gradual from ~1.0km/s (at sin\theta = 0:
disk center) to ~1.3km/s (at sin\theta ~ 0.7: two-thirds of radial distance);
but thereafter increasing more steeply up to ~2km/s (at sin\theta = 0.97:
limb). This result further suggests that the microturbulence derived from the
flux spectrum of the disk-integrated Sun is by ~20% larger than that of the
disk-center value, which is almost consistent with the prediction from 3D
hydrodynamical model atmospheres.
