  A derivation of the asymptotic expressions for the threshold intensity of
laser induced thermal scattering in silica microresonator when illuminated with
a plane wave is present. The calculation of anti-Stokes thermal combination
frequencies are made for the spherical high Q-factor microresonators. The three
modes regime of nonlinear interaction is considered. One pump-driven, two
signal modes, and one mode of temperature relaxation are taken into account,
satisfying morphology-dependent input and output resonances. There are low
power thresholds for laser induced thermal scattering at morphology dependent
resonances.
