  Neutrino oscillations, biased by the magnetic field, alter the shape of the
neutrinosphere in a cooling protoneutron star emerging from the supernova
collapse. The resulting anisotropy in the momentum of outgoing neutrinos can be
the origin of the observed proper motions of pulsars. The connection between
the pulsars velocities and neutrino oscillations results in a prediction for
the tau neutrino mass of order 100 eV.
