  The bulk of the quiet solar photosphere is thought to be significantly
magnetized, due to the ubiquitous presence of a tangled magnetic field at
subresolution scales with an average strength <B> ~ 100 G. This conclusion was
reached through detailed three-dimensional (3D) radiative transfer modeling of
the Hanle effect in the Sr I 4607 line, using the microturbulent field
approximation and assuming that the shape of the probability density function
of the magnetic field strength is exponential. Here we relax both
approximations by modeling the observed scattering polarization in terms of the
Hanle effect produced by the magnetic field of a 3D photospheric model
resulting from a (state-of-the-art) magneto-convection simulation with surface
dynamo action. We show that the scattering polarization amplitudes observed in
the Sr I 4607 line can be explained only after enhancing the magnetic strength
of the photospheric model by a sizable scaling factor, F=10, which implies <B>
= 130 G in the upper photosphere. We argue also that in order to explain both
the Hanle depolarization of the Sr I 4607 line and the Zeeman signals observed
in Fe I lines we need to introduce a height-dependent scaling factor, such that
the ensuing <B> = 160 G in the low photosphere and <B> = 130 G in the upper
photosphere.
