  We analyze numerically the correspondence between the mechanical action,
experienced by a spherical microparticle, and the internal energy flows as well
as spatial and polarization inhomogeneity of the light field incident on the
particle. The inhomogeneous incident field is modelled by superposition of two
plane waves, the mechanical action is calculated via the Mie theory for
dielectric and conducting particles of different sizes and optical properties.
It is shown that both spin and orbital components of the field momentum can
produce the mechanical action, which can thus be used for experimental study of
the internal energy flows in light beams. However, exact value and even
direction of the force applied to a particle depends on many details of the
field-particle interaction. Besides, forces that are not associated with any
sort of the energy flow (we attribute them to the gradient force owing to the
inhomogeneous intensity and to the dipole force emerging due to inhomogeneous
polarization) can strongly modify the observed mechanical action. The results
should be taken into account in experiments employing the motion of probing
particles suspended within optical fields. We suppose that situations where an
optical field exerts the polarization-dependent mechanical action on particles
can be treated as a new form of the spin-orbit interaction of light.
