Energy exchange processes between electrons and photons in the strong radiation fields encountered in some astrophysical objects. I

On the basis of an analysis of studies made of single-photon Compton interaction between electrons and photons and its importance in the interpretation of the observational data on a number of astrophysical objects (nuclei of Seyfert galaxies, quasars, interstellar masers, the pulsar NP 0532, radio pulsars), three classes of fundamental problems are identified: A,B,C. It is shown that under the physical conditions existing in these astrophysical objects it is also necessary to take into account many-photon Comptonization processes, since the efficiency of these may be appreciably greater than that of the single-photon processes (for example, for the pulsar NP 0532 and for radio pulsars by one and two orders of magnitude). The present paper is devoted to a particular A problem - the relaxation of a nonequilibrium isotropic radiation field interacting with a nonrelativistic nondegenerate equilibrium electron gas through many-photon Compton scatterings. The introduction and use of a new concept, the ''effective photon,'' makes it possible to obtain a kinetic equation that describes the variation in time of the photon distribution function. By a direct calculation of the change in the total entropy of the electron-photon system it is shown that the kinetic equation satisfies Boltzmann's H theorem. Equations that describe the variation in time of the total exchange energy and the heating and cooling of the electron gas are also obtained