This is a theoretical investigation on the formation of the linearly
polarized line spectrum of ionized cerium in the sun. We calculate the
scattering line polarization pattern emergent from a plane-parallel layer of Ce
{\sc ii} atoms illuminated from below by the photospheric radiation field,
taking into account the differential pumping induced in the various magnetic
sublevels by the anisotropic radiation field. We find that the line
polarization pattern calculated with this simple model is in good qualitative
agreement with reported observations. Interestingly, the agreement improves
when some amount of atomic level depolarization is considered. We find that the
best fit to the observations corresponds to the situation where the ground and
metastable levels are depolarized to about one fifth of the corresponding value
obtained in the absence of any depolarizing mechanism. One possibility to have
this situation is that the depolarizing rate value of elastic collisions is
exactly $D=10^6{\rm s}^{-1}$, which is rather unlikely. Therefore, we interpret
that fact as} due to the presence of a turbulent magnetic field in the limit of
saturated Hanle effect for the lower-levels. For this turbulent magnetic field
we obtain a lower limit of 0.8 gauss and an upper limit of 200-300 gauss.