  Neutrinos propagating in media (matter and electromagnetic fields) undergo
flavor and helicity oscillations, where helicity transitions are instigated
both by electromagnetic fields and matter currents. In addition, it has been
shown that correlations between neutrinos and antineutrinos of opposite
momentum can build up in anisotropic media. We re-derive the neutrino equations
of motion in the mean-field approximation for homogeneous yet anisotropic
media, confirming previous results except for a small correction in the
Majorana case. Furthermore, we derive the mean-field Hamiltonian induced by
neutrino electromagnetic interactions. We also provide a phenomenological
discussion of pair correlations in comparison with helicity correlations.
