  The cross sections for the processes \gamma \nu --> \gamma\gamma \nu,
\gamma\gamma -->\gamma\nu\bar{\nu} and \nu\bar{\nu} -->\gamma\gamma\gamma are
calculated with the aid of an effective Lagrangian derived from the Standard
model. These cross sections are shown to be much larger than the elastic cross
section \sigma(\gamma\nu --> \gamma\nu) for photon energies $\omega > 1$ keV.
Possible astrophysical implications are discussed.
