Neutrino self-polarization effect in matter

The quasi-classical theory of the spin light of neutrino ($SL\nu$) in background matter, accounting for the neutrino polarization, is developed. The neutrino transitions $\nu_{L}\to \nu_{R}$ and $\nu_{R}\to \nu_{L}$ rates in matter are calculated. It is shown that the $SL\nu$ in matter leads to the neutrino conversion from active $\nu_{L}$ to sterile $\nu_{R}$ states (neutrino self-polarization effect in matter).