  The radiometric force on a sphere due to its thermal polarization in a
rarefied gas flow being in equilibrium is investigated on the basis of a
kinetic model to the linearized Boltzmann equation. The scattering kernel
proposed by Cercignani and Lampis to model the gas-surface interaction using
two accommodation coefficients, namely the tangential momentum accommodation
coefficient and the normal energy accommodation coefficient, is employed as the
boundary condition. The radiometric force on the sphere, as well as the flow
field of the gas around it, are calculated in a wide range of the gas
rarefaction, defined as the ratio of the sphere radius to an equivalent free
path of gaseous particles, covering the free molecular, transition and
continuum regimes. The discrete velocity method is employed to solve the
kinetic equation numerically. The calculations are carried out for values of
accommodation coefficients considering most situations encountered in practice.
To confirm the reliability of the calculations, the reciprocity relation
between the cross phenomena is verified numerically within a numerical error of
0.1%. The temperature drop between two diametrically opposite points of the
spherical surface in the direction of the gas flow stream, which characterizes
the thermal polarization effect, is compared to experimental data for a
spherical particle of Pyrex glass immersed in helium and argon gases.
