  We calculate the transition radiation process $\nu \to \nu \gamma$ at an
interface of magnetic field and vacuum. The neutrinos are taken to be with only
standard-model couplings. The magnetic field 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. The neutrino mass is
ignored due to its negligible contribution. We present a result for the
probability of the transition radiation which is both accurate and analytic.
