  The photon-neutrino processes $\gamma e^{\pm} \to e^{\pm} \nu \bar \nu$,
$\gamma \to \nu \bar \nu$ and $\gamma \gamma \to \nu \bar \nu$ are investigated
in the presence of a strongly magnetized and dense electron-positron plasma.
The amplitudes of the reactions $\gamma e^{\pm} \to e^{\pm} \nu \bar \nu$ and
$\gamma \gamma \to \nu \bar \nu$ are obtained. In the case of a cold degenerate
plasma contributions of the considering processes to neutrino emissivity are
calculated. It is shown that contribution of the process $\gamma \gamma \to \nu
\bar \nu$ to neutrino emissivity is supressed in comparision with the
contributions of the processes $\gamma e^{\pm} \to e^{\pm} \nu \bar \nu$ and
$\gamma \to \nu \bar \nu$. The constraint on the magnetic field strength in the
magnetar outer crust is obtained.
