Photon-neutrino interactions in magnetic fields

The low-energy two neutrino-two photon interactions in the presence of homogeneous magnetic field are studied. The cross sections in external magnetic field are shown to be larger than in vacuum by factor $\sim (m_W /m_e) ^4(B/B_c) ^2$\mathrm{.}Theenergy-lossrateduetotheprocess$\gamma \gamma \to \nu \bar{\nu}$ in magnetic field is obtained.