There are two main neutrino driven kick scenarios, relying on the parity violation of neutrino interactions to explain an asymmetry in neutrino distribution. The first uses the fact that in the presence of a magnetic field, the direction that a neutrino is scattered off a nucleus is biased in some direction. So if neutrino emission happened in the presence of a strong magnetic field, we might expect the average neutrino drift to align in some way with that field, and thus the resulting explosion would be asymmetric. A main problem with this theory is that to have sufficient asymmetry the theory requires fields of order 1015 G, much stronger than is expected in a heavy star. Another neutrino based theory uses the fact that the cross section for neutrino scattering depends weakly on the strength of the ambient magnetic field. Thus, if the magnetic field is itself anisotropic, then there could be dark spots which are essentially opaque to neutrinos. This however requires anisotropies of order 1016 G, which is even more unlikely.