We discuss the transition radiation process ν→νγ at an
interface of two media. The medium fulfills the dual purpose of inducing an
effective neutrino-photon vertex and of modifying the photon dispersion
relation. The transition radiation occurs when at least one of those quantities
have different values in different media. We present a result for the
probability of the transition radiation which is both accurate and analytic.
For Eν​=1MeV neutrino crossing polyethylene-vacuum interface the
transition radiation probability is about 10−39 and the energy intensity
(deposition) is about 10−34eV. At the surface of the neutron stars the
transition radiation probability may be ∼10−20. Our result on three
orders of magnitude is larger than the results of previous calculations.}Comment: invited talk, to appear in the proceedings of the XLVIth Rencontres
de Moriond EW 201