  We propose to model the uppermost inner core as an aggregate of randomly
oriented anisotropic ``patches''. A patch is defined as an assemblage of a
possibly large number of crystals with identically oriented crystallographic
axes. This simple model accounts for the observed velocity isotropy of short
period body waves, and offers a reasonable physical interpretation for the
scatterers detected at the top of the inner core. From rigorous multiple
scattering modeling of seismic wave propagation through the aggregate, we
obtain strong constraints on both the size and the elastic constants of iron
patches. We perform a systematic search for iron models compatible with
measured seismic velocities and attenuations. An iron model is characterized by
its symmetry (cubic or hexagonal), elastic constants, and patch size.
Independent of the crystal symmetry, we infer a most likely size of patch of
the order of 400 m. Recent {\it bcc} iron models from the literature are in
very good agreement with the most probable elastic constants of cubic crystals
found in our inversion. Our study (1) suggests that the presence of melt may
not be required to explain the low shear wavespeeds in the inner core and (2)
supports the recent experimental results on the stability of cubic iron in the
inner core, at least in its upper part.
