Pulsar Kicks from Asymmetric Neutrino Transport

In magnetized proto-neutron stars, neutrino cross sections depend asymmetrically on the neutrino momenta due to parity violation in the weak interaction. As a consequence, neutrinos escaping from the collapsed core will develop a flux along the direction of the magnetic field in addition to the usual (spherical) diffusive flux. The neutron star will recoil opposite the direction of this asymmetric flux. We find that quite large magnetic fields B ~ 10(15}-10({16)) G are needed to produce recoil velocities of order a few hundred km s(-1) . Hence, the parity violation effect can only produce large space velocities for a relatively small percentage of the pulsar population with extremely large magnetic fields.