  We discuss the transition radiation of a neutrino induced by its toroid
dipole moment ($\tau$) when crossing the interface between two different media
with different refraction indices. A neutrino of 1 MeV energy emits
approximately $10^{-40}$ keV at $\tau=e\sqrt{2}G_F/\pi^2$. This effect depends
very slightly on the neutrino mass and has a finite value in the massless
limit.
