Asymptotical photon distributions in the dissipative dynamical Casimir effect

Asymptotical formulae for the photon distribution function of a quantum oscillator with time-dependent frequency and damping coefficients, interacting with a thermal reservoir, are derived in the case of a large mean number of quanta. Different regimes of excitation of an initial thermal state with an arbitrary temperature are considered. New formulae are used to predict the statistical properties of the electromagnetic field created in the experiments on the dynamical Casimir effect that are now under preparation.