  As is well known that the distribution of the scattered radiation generated
by an anisotropic scatterer usually lacks rotational symmetry about the
direction of incidence due to the spatial anisotropy of the scatterer itself.
Here we show that the rotationally symmetric distribution of the far-zone
scattered momentum flow may be realized provided that the structural parameters
of both the medium and the source are chosen suitably, when a polychromatic
electromagnetic plane wave is scattered by an anisotropic Gaussian Schell-model
medium. We derive necessary and sufficient conditions for producing such a
symmetric distribution, and further elucidated the relationship between the
spectral degree of polarization of the incident source and the rotationally
symmetric momentum flow of the scattered field in the far zone. It is found
that the realization of the rotationally symmetric scattered momentum flow is
independent of the spectral degree of polarization of the source, i.e., the
rotationally symmetric distribution of the far-zone scattered momentum flow is
always realizable regardless of whether the incident source is fully polarized,
partially polarized or completely unpolarized. Our results may find useful
application in optical micromanipulation, especially when the optical force
used to manipulate particles requires to be rotationally symmetric.
