Effect of external field on coherent backscattering in nematics

For a one-elastic-constant model of nematic liquid crystal the optical theorem is shown to produce an explicit relationship between the scattering length of extraordinary wave mode and magnetic coherence length. The Monte Carlo simulation of coherent backscattering is performed accounting for the long-range orientational fluctuations and scattering length anisotropy; the coherent backscattering peak is shown to change quite weakly while the magnetic field varies several orders.