Energy Transfer in the Earth's Mantle

Several processes of energy transfer in the earth's mantle are examined: (1) gray radiation, (2) ambipolar diffusion of electron-hole pairs, (3) exciton transfer, and others. Using Rikitake's values of the electrical conductivity and correcting for the frequency dependence of the conductivity and the variation of the index of refraction with depth, the values for the radiative contribution to the heat flow are found to be appreciably larger than those estimated by Clark. Estimation of contributions from the electronic processes shows that conduction by excitons may play an important role in the lower parts of the mantle.