PHYSICS OF NONMAGNETIC RELATIVISTIC THERMAL PLASMAS (ASTROPHYSICS, RELATIVITY, ATOMIC PROCESSES)

A detailed treatment of the kinematics of relativistic systems of particles and photons is presented. In the case of a relativistic Maxwell-Boltzmann distribution of particles, the reaction rate and luminosity are written as single integrals over the invariant cross section, and the production spectrum is written as a double integral over the cross section differential in the energy of the produced particles (or photons) in the center-of-momentum system of two colliding particles. The result is valid for all temperatures and for the general case when the plasma contains different mass particles.;The question of thermalization of a relativistic plasma is considered. A formula for the energy loss or exchange rate from the interaction of two relativistic Maxwell-Boltzmann plasmas at different temperatures is derived. It is concluded that at temperatures greater than about 1 MeV, full thermalization of an electron-proton plasma is not possible because of the dominance of bremsstrahlung losses.;Application to a stable, uniform, nonmagnetic relativistic thermal plasma is made. Approximate expressions for dominant rates, taking account of the effects of Comptonization, are used to model the system at extreme relativistic temperatures and at sub-relativistic temperatures in the limit of large optical depth. Equilibrium pair densities, critical temperatures, and emergent spectra are calculation. Comparison is made with other studies.;The results are applied to the calculation of the annihilation spectrum of a thermal electron-positron plasma, confirming previous numerical and analytic results. Relativistic thermal electron-ion and electron-electron bremsstrahlung are calculated exactly to lowest order, and relativistic thermal electron-positron bremsstrahlung is calculated in an approximate way, by interpolating between the modified Bethe-Heitler formula and the exact lowest order electron-electron bremsstrahlung spectrum. An approximate treatment of relativistic Comptonization is developed.