  The R^{2}-gravity contribution to energy loss of a hot plasma due to the
gravitational bremsstrahlung is calculated in the linearized theory on the
basis of classical Coulomb scattering of plasma constituents in small-angle
scattering approximation. The explicit dependence of the gravitational
luminosity on the plasma temperature is derived and its relevance to the
Einstein gravity is demonstrated. The result when applied to the Sun as a hot
plasma, shows very good agreement with available data.
