REGULAR AND STOCHASTIC ACCELERATION OF PHOTONS

The Hamiltonian formulation of ray tracing trajectories is used to describe the various mechanisms of photon acceleration. This leads to a straightforward derivation of the frequency shifts and of the time and length scales. The existence of three types of photon trajectories, in the presence of an ionization front, is demonstrated. A threshold condition for transition from regular to stochastic photon acceleration is also derived.