Spectral energy distribution of the equilibrium radiation and its asymptotic behavior in ideal gaseous plasmas

Abstract

It is shown that the difference between the Planck distribution and the spectral energy distribution of the equilibrium radiation in a homogeneous and isotropic material medium is completely determined by the transverse dielectric permittivity of the material medium. In contrast with the well known approach for the generalized spectral energy distribution of the equilibrium radiation in a plasma medium based on accounting only the frequency dependence of the dielectric permittivity, the crucial role of both the frequency and the spatial dispersions of the transverse dielectric permittivity is demonstrated. On this basis, the high-frequency and the low-frequency asymptotical properties of the spectral energy distribution in an ideal gaseous plasma are considered. The obtained results for the equilibrium spectral distribution are principally different from the corresponding asymptotic of the Planck distribution, possessing a long tail at the high frequency and a logarithmical increase at the low frequency.