photon emissivity of strange matter is very low. For temperatures $T<<E_{p} $, where $E_{p}\approx 23$ MeV is the characteristic transverse plasmon cutoff energy, the equilibrium photon emissivity of strange matter is negligibly small, as compared to the blackbody one. The spectrum of equilibrium photons is very hard, with $\omega
>20$ MeV [@Chm91].

The bremsstrahlung emissivity of the quark matter and of the electrosphere have been estimated recently in @ChHa03 [@Ja04; @HaCh05]. By taking into account the effect of the interference of amplitudes of nearby interactions in a dense media (the Landau-Pomeranchuk-Migdal effect) and the absorption of the radiation in the external electron layer, the emissivity of the quark matter could be six orders of magnitude lower than the equilibrium blackbody radiation [@ChHa03]. The presence of the electric field strongly influences the radiation spectrum emitted by the electrosphere and strongly modifies the radiation suppression pattern [@HaCh05]. All the radiation properties of the electrons in the electrosphere essentially depend on the value of the electric potential at the quark star surface.

The Coulomb barrier at the quark surface of a hot strange star may also be a powerful source of $e^{+}e^{-}$ pairs, which are created in the extremely strong electric field of 